I also hope to find out - FFEL Program. Are only FFEL Program loanseligible for Income-Sensitive Repayment Plan?
Yes, only FFEL Program Loans are eligible.
I also hope to find out, aside from  Federal Family Education Loan Program, what other loans do other places handle for you?
The U.S. Department of Education also uses several loan servicers to handle the billing and other services on loans for that were made under the Federal Family Education Loan Program and that ED later purchased .