Mother and son relation for gift deed

Dear all, My friend whose mother was retired from Govt. service. She got money of Rs.13 lacs from her services. She wants to give 10 lacs to his son who wants to buy flat from that amount. Queries 1. Can his mother make gift deed o when she gives money to her son? 2. Is there any amount limit for gift deed as per income tax rule? 3. whatever amount will received by mother. Is it taxable to her son? Many thanks in advance 1