Dear Sir,
No you don't have option to pay LTCG tax, with indexation or without indexation ,whichever is lesser.
LTCG will be payable using indexation.
Yes, GAAR should not apply on this transaction.
No, there is not inheritance tax in India for agriculture land.
Please feel free to call/revert in case of any doubts
Thanks and Regards
Abhishek Dugar
CA CS B.Com