All types of debt instruments viz. Bonds, Debentures, Commercial Papers, Certificates of Deposit, Government Securities (Gsec) etc. irrespective of whether these instruments are listed / unlisted / privately placed can be dematerialised with CDSL, if they had been admitted with CDSL.
CDSL has also provides the facility of maintaining warehouse receipts pertaining to commodities in dematerialised form.

Yes. Debt instruments, mutual fund units, government securities can also be dematerialised in the same demat account where equities are held.

Investors and brokers are required to open sperate demat accounts for holding warehouse receipts. These accounts can be used only for holding warehouse receipts.