Extra-ordinary Leave to Permanent Employee [CCS Leave Rule – 32(1)]
Extraordinary leave (subject to maximum limit as per Rule-12, i.e. 5 years) may be granted to a Government servant (other than a military officer) in special circumstances-
(a)        When no other leave is admissible.
(b)        When other leave is admissible, but the Government servant applies in writing for the grant of extraordinary leave.

2)Twenty-four months, where the leave is required for the purpose of prosecuting studies certified to be in the public interest, provided the Government servant concerned has completed three years’ continuous service on the date of expiry of leave of the kind due and admissible under these rules, including three months’ extraordinary leave under Clause (a).

3.         Requirement of Bond [CCS Leave Rule – 32(3)]
(a) Where a temporary Government servant is granted extraordinary leave for the purpose of prosecuting studies, shall be required to execute a Bond in Form 6 undertaking to refund to the Government the actual amount of expenditure incurred by the Government during such leave plus that incurred by any other agency with interest thereon in the event of his not returning to duty on the expiry of such leave or quitting the service before a period of three years after return to duty.
(b) The Bond shall be supported by Sureties from two permanent Government servants having a status comparable to or higher than that of the Government servant.

1. Extraordinary leave can be granted when no other leave is admissible.

2. It can also be granted when any other kind of leave is admissible but the member of the Service applies in writing for the grant of extraordinary leave.

3. You can apply for EOL but it is the prerogative of govt.

Dear Sir,

Normally educational leave will be granted to the extent of 24 months beyond that you have to seek special permission from the department if rejected you have to approach High Court to get appropriate relief.

As per the provisions of All India Services (Study leave ) regulations, 1960:

3(4) Study leave shall not be granted to a member of the Service—
3(4) (i) who has rendered less than „seven years‟ service under the Government:
Provided that the All India Service Officers borne on the North East Cadres of Assam-Meghalaya, Manipur-Tripura, Nagaland and Sikkim shall be eligible for the study leave after completion of six years‟ service under the Government.

4. Maximum amount of study leave that may be granted at a time and during
the entire service.— The maximum amount of study leave, which may be granted to a
member of the Service, shall be—
4(i) ordinarily twelve months at any one time, which shall not be exceeded save for exceptional reasons; and
4(ii) twenty-four months (inclusive of study leave granted under any other rules) in all during his entire service:
Provided that the All India Service Officers selected for fellowships approved by the Government of India, from time to time, by general or special orders, will be granted study leave for the entire period of fellowship, not exceeding twenty-four months.
5. Combination of study leave with leave of other kinds.—
105(1) Study leave may be combined with other kinds of leave, but in no case shall the grant of this leave in combination with leave other than extraordinary leave, involve a total absence of more than twenty—eight
months generally and thirty—six months for the courses leading to Ph.D degree from the regular duties of the member of the Service.
Explanation:— The limit of twenty-eight months or thirty-six months of absence prescribed in this sub-regulation includes the period of vacation.

you want to obtain extraordinary leave for further studies 

you have stated you are permanent employee 

you would be required to execute bond even if it is for extraordinary leave as you want to do further studies 

Government servant is required to execute a bond to serve the Government for a period of three years after expiry of study leave. For CHS officers
theperiodis fiveyears.(Rule55)

Leave is a provision to stay away from work for genuine reasons with prior approval of the authorities. It may be granted for a casual purpose or a planned activity, on medical grounds or in extra-ordinary conditions.

As you have rightly mentioned that there is no provision for permanent employees in the CCS or any other leave regulation of the central government granting  the employee EOL for the purpose of pursuing higher studies, you cannot insist on any such non-existing rules or regulations to suit to your taste. 

You cannot avail both the benefits together i.e., the employment as well as higher studies together if you are not having qualifying service to avail the said benefits. 

Dear Sir,

After completion of 5 years continuous service, you are eligible for study leave. Except Central Health Service Officers, maximum amount of study leave granted is 12 months at any one time and 24 months during entire service.

THE ALL INDIA SERVICES (STUDY LEAVE)
REGULATIONS, 1960

Section 3. Conditions for grant of study leave.—
3
3(1) Subject to the conditions prescribed in these regulations, study leave may
be granted to a member of the Service, with due regard to the exigencies
of public service, to enable him to undergo, in or out of India—
3(1) (i) a special course of study consisting of higher studies or specialised
training in a professional or technical subject having a direct and close
connection with the sphere of his duty; or
3(1) (ii) a course of training or study tour, where such course of training or
study tour is related to the sphere of his duties even though he/she
may not attend a regular academic or semi-academic course; or
3(1) (iii) studies connected with the framework or background of public
administration; or
3(1) (iv) studies which may not be closely or directly connected with the work
of the member of the Service, but which are capable of widening his
mind in a manner likely to improve his ability as a civil servant and to
equip him better to collaborate with those employed in other branches
of public service:

Provided that the grant of study leave under clauses (ii) and (iii) shall be subject to
the following conditions, namely:—
(a) that the particular course of training, study or study tour is approved
by the authority competent to grant study leave; and
(b) that the member of the Service is required to submit, on his return, a
full report on the work done by him while on study leave.
Note.— Applications for study leave falling under clause (iv) shall be considered
on merits of each case, in consultation with the Central Government.
3(2) Study leave shall not be granted unless—
3(2) (i) it is certified by the Government that the proposed course of study or
training shall be of definite advantage from the point of view of public
interest; and
3(2) (ii) it is for prosecution of studies in subjects other than academic or
literary subjects.
4
3(3) Study leave out of India shall not be granted—
3 (3) (i) without the prior approval of the Central Government; and
3(3) (ii) for the prosecution of studies in subjects for which adequate facilities
exist in India or under any of the Schemes administered by the
Government of India.
3(4) Study leave shall not[ ]5
be granted to a member of the Service—
3(4) (i) who has rendered less than „seven years‟ service under the
Government:
6Provided that the All India Service Officers borne on the North East
Cadres of Assam-Meghalaya, Manipur-Tripura, Nagaland and Sikkim
shall be eligible for the study leave after completion of six years‟
service under the Government; and
7
3(4) (ii) who is due to reach the age of superannuation within three years from
the date on which he is expected to return to duty after the expiry of
leave.
3(5) Study leave shall not be granted to a member of the Service with such
frequency as to remove him from contact with his regular work or to
cause cadre difficulties owing to his absence on leave.
8
3(6) Where a member of the Service borne permanently on the cadre of one
State is serving, temporarily in another State or under the Central
Government, the grant of study leave shall be subject to the condition that
the concurrence of the State Government, on whose cadre he is
permanently borne, is obtained before the leave is given.