Suit fule

There is no difference between a "secured" and "unsecured" loan for its recovery and a suit for recovery can be filed and decreed, if properly evidenced / proved.

Prsumably it is an examination type of query, which should have been guided by your professor / coach / tutor, if so.

Yes, suit can be filed but plaintiff has to prove the contents of suit by cogent evidence. 

If the legal heirs have inherited the assets/properties from the deceased borrower then they can be made liable to repay the loan to the extent of the property benefits availed by them.