1) you cannot send your resignation directly to directorate without reporting back for duty
2) you cannot resign without previous permission of commandment
3) you have to give 3 months notice if you want to resign from service
4) rule 6 :
6. Resignation and withdrawal from the Force.—No member of the Force shall be at liberty to—
(a) resign his appointment during the term of his engagement, except before the expiration of the first three months of his service; or
(b) withdraw himself from all or any of the duties of his appointment, without the previous permission in writing of the Commandant or Assistant Commandant or any other officer authorised by the Commandant to grant such permission.
After you have served in the Force for such period as the Central Government may prescribe, you may, at any time when not on active duty, apply for discharge, through the officer to whom you may be subordinate to the Commandant, and you will be granted your discharge after two months from the date of your application, unless your discharge would cause the vacancies in the Force to exceed one-tenth of the sanctioned strength in which case you shall be bound
Provided that, if you wish to withdraw from the Force, you may submit your resignation at any time before the expiration of the first three months of your service, but not afterwards until the completion of the period prescribed as aforesaid the Commandant may either accept your resignation forthwith or at the end of three months from the date of its receipt:
Provided, also, that the Commandant may, if he thinks fit, allow you to resign at any time on your giving three months notice of your wish to do so