Can Inventory Management or Stock tracking be done in Kentico9 ???

I would say the save answer is, yes.

Kentico 8's Ecommerce API increased greatly from 7, so 8 and 9 both have a much more flexible API interface for pretty much all systems. I've in the past used it to create product variants on the fly and such, setting inventory stock and getting it shouldn't be too hard of a process.

Check out the Products documentation, it shows in there you can do some pretty good inventory tracking. Your needs may be different but the answer to your question is yes.