Capital gain

Since this is a personal thing,  yes. A loss can be set off from other sources of income.

It’s properly defined in section 70(1,2 &3). A) Since debentures are capital in nature but debt instrument, at amortised cost while the carry forward loss can be from speculation. B) If that is also a traded version, you can set off. Not sure about the option A. 

https://learn.quicko.com/income-tax-bonds-debentures

What about issued debentures after amortisation? I guess that will not be considered as things are different between company and personal accounting