what do you mean by authorized/unauthorized?

if you are asking about the area, you can confirm from the municipality or the Town Planning office

your query is not clear

If you have purchased the proeprty by a registered sale deed that too after obtaining a proper legal opinion, what is is your worry about it.

The registered sale deed will confer title to you on the property you purchased. 

Three floors on 100 gaj is illegal construction. But demolition may not done. If 3 floors are constructed than all 3 floor owners have 33% ownership in land.

Rest 100 gaj is using for parking for floors owner only - right.

Whether construction has been done as per sanctioned plans ? 

whether any completion certificate has been issued ? 

kindly clarify 

If construction is unauthorised it can be demolished by muncipal corporation 

At least now you can refer the matter to a local advocate and obtain a proper opinion and suggestion  to move ahead on the basis of documents and other relevant papers in your possession. 

Any proper opinion in furtherance can be rendered only after scrutinizing the property papers. 

Dear Sir

Please check from office of registrar about the genuineness of the matter

Hi

Your property is authorized and its all good if you brought it via a registered sale deed.

Single plot can be sold in parts

You can sell the same in partition if you want. But you need to legally do the same by partitioning the said property. It perfectly legal

1. Even IF the property (house) is unauthorized, you can submit proper documentations to the Municipal /Revenue authorities to regularize it by paying relevant penalty etc.... 

2. Residential Property CANNOT be demolished until proper notice and notice period is given to the house occupant. When you receive notice, THEN using the services of a local architect, conduct above point no. 1.

Firstly, it needs to be seen whether the said construction is carried out after obtaining  permission from concerned.

Whether any deviation is there if permission is obtained.

It the construction is unauthorized, there is likelihood of demolition by Department.

Immediately check the above, if permission is not there, you can apply for regularization of the said construction.

please search that the builder or the owner had obtained the necessary permission for the local concerned authority and also check the sanction plan and permission of built up area.

you are advised to contact a local lawyer and take legal assistance from him .

The property is authorized or not you can easily come to know from the Delhi Municipal corporation sanctioned layout plan of Building in its all details are mentioned accordingly the floor wise built up sq ft area.

See the documents and chain document need to be seen and perused for same. If plans are sectioned and the registered deed is signed along availability of all chain documents it is likely to be authorised.

If the demarcation is proper he can sale though in your case it is better to contact a local lawyer with all documents.

1. Unless the property documents which form a part of the chain of title are perused threadbare nobody can tell you if the title passed to you is free and marketable. It is trite law that nobody can pass a title better than his own title. You ought to have conducted due diligence before purchasing.

2. Consult a lawyer with all the documents.

1. Property can be sold by dividing in two parts.

2. The property can be unauthorized if builder have constructed the property without approval from town planning deparment.

The construction  of the property should be checked with the municipal corporation of Delhi. A map must be present and it should have been passed by the MCD.

Check it out with the municipal corporation. See the rules governing the construction of the property. Otherwise engage an architect who knows about this.