1. It appears the gun was deposited under Rule 46 of Arms Rules 1962.
2. I do not think arms licenses are transferable. Apply for arms license in your name under family heirloom. You would also need to submit no objection certificates from all legal heirs. Once you get the license, get the shotgun released and endorsed on your license.
3. Non income tax payees or unemployed can get arms license. Read Sections 13 and 14 of Arms Act 1959 carefully.
Please use the search box on upper right hand corner to search this forum, these questions have already been explained in detail at number of places. If something is not already discussed in this forum feel free to ask.
All things are subject to interpretation whichever interpretation prevails at a given time is a function of power and not truth. - Friedrich Nietzsche