1) Section 420 is a non-bailable offence but if you have some good grounds in your defense, you will surely get the bail.
2) No, Service and Your ancestral property transactions nothing to do with it, so don't mix it up
3) No, you can take POA to attend all legal matters on behalf of her.
4) If FIR is raised against you otherwise not
5) Whatsoever your mother has taken decision that is right to compromise for 1/4th share, if that property is your father self earned than don't worry at all.
6) Instead of giving share in plot ask your grandmother to take money which you have received in the selling year.
There are so many options related to your case and turn your case in your favor without going to court.