Торба should be accepted. Сумка is a russian word
Do you know that Ukrainian city Sumy and word сумка share the same origin? :) And ever heard of сумчасті?
That may be so indeed. Regardless, my point is that торба should be accepted
I am not sure that they are the same thing: http://sum.in.ua/s/torba
Can i not use ця here?
Nope. In sentence like "This is a horse", "It is my brother", "That's not a problem" you always use це at the beginning, and it does not change at all.
Isn't a backpack a bag?