1. Your grandmother is free to transfer her property during her lifetime to anyone. She can execute a gift deed which will result in an instantaneous transfer of property from her to donee. If she makes a will then it will come into operation after her lifetime.

2. If she dies intestate then her property will devolve through intestate succession on her children after her death. You are not a legal heir to your grandmother during the lifetime of your father. Hence, you will not succeed to the property even if you have been looking after her.

1) you have not mentioned whether property is independent house or flat in cooperative housing society 

2) if it is flat in housing society your grand mother can fill in nomination form in your favour . As you are the only legal heir society can on grand mother demise transfer flat in your name on basis of nomination form 

3) if it is independent house on grand mother demise apply for mutation of property in your name 

4) enclose grand mother death certificate, latest receipt of payment of property taxes, 

5) you can apply for letters of administration from district court if grand mother died intestate if insisted upon by revenue authorities 

It is advisable that gift deed be executed during grand mother lifetime 

it should be duly stamped and registered 

3) it attracts concessional rate of stamp duty if executed in favour of family member 

4) contact a local lawyer 

 1. If your grandmother dies intestate, then the property would devolve to you only, as your father was the only child to her, as well as you are the only child to your deceased parents.

2.  After her death, you have to get the property in your name mutated in the jurisdictional Corporation/Municipal Office by applying for the same in the prescribed application form enclosing her death certificate and legal heirship Certificate/Genealogical Tree (Family Tree).

3.  During her lifetime itself, she can gift the property to you by executing a registered Gift Deed in the jurisdictional Sub Registrar's Office.

Stamp Duty for registering the Gift Deed amongst blood relatives is very nominal. For example in Karnataka, the stamp duty for registering the Gift Deed amongst blood relatives is only around Rs. 5000/- only. Please check in your place.

1.  If your grandmother is not making any Will bequeathing the proeprty to your name, then the property shall devolve equally on her legal heirs.

Since your father was the only child to your grandmother and he is also no more living, then the property left behind by your grandmother upon her intestate death shall devolve on the legal heirs of her deceased legal heir, i.e., you. 

You can get a legal heirship certificate of your deceased father and your grandmother  also after which you can submit an application to transfer the revenue records to your name, subsequent to which you will become an absolute owner of the proeprty left behind by your grandmother. 

2. Yes the registered gift deed on the name of your grandmother shall be the title document to declare her title to the property.

3. You would require the original registered gift deed standing in the name of your grandmother, the document by which the donor gifted this property to your grandmother, tax paid receipts, patta, the death certificate of your father, legal heirship certificate in respect of your father and that of your grandmother too. 

If it is not possible to transfer the property to your name by a registered gift deed, you may ask her to transfer the same by a testamentary disposition i.e., by making a Will bequeathing the property to you which will come into force on her death.

This is not cost involved. 

1. After the demise of your grandmother intestate, under the given circumstances, you shall automatically inherit all her properties being her sole legal heir.

2. If the said gift deed was registered then she will be considered as the title holder of the said gifted property.

3. After her demise intestate, you shall have to obtain the legal heir certificate from the Ward Counselor of your Municipal Corporation to establish that you are the sole legal heir of your grandmother.

Dear sir 

You are required to have succession certificate and it will solve the purpose. 

Other than will you need to seek heirship certificate from court. 

Yes registered gift deed is fine

1. Registration fee, if any, should be nominal.

2. Get the gift deed drafted by a lawyer.

1. Since you alone are legal heir of your grandmother on her death by law of Succession you inherit all her properties. 

2. To do this you need to make an affidavit and Mutate the house in your name. 

3. If there is lack of documentary evidence to show your relationship with your grandmother then either make a Will or get a gift deed registered in your name.