Regarding MFI

Yes, you can run a Micro finance institution under a trust. In this case you don't need to take any registration from RBI but you have to follow RBI guidelines.

and later on if you want to start a NBFC MFI, then trust are not allowed to start NBFCs. A NBFC should be a company registered under Companies Act. In that case you have to convert your Trust to section 8 company.

Thanku Sir