How do remove vinyl cove base from the bottom of kitchen cabinets

It might be glued on, or nailed on. Most likely glued. Which means... VERY carefully... if particle board is used it can get really ugly depending on how well its glued and what type is used as well as how much, and all but the better custom and semi-custom cabinets are likely to use it.

It is all the this you listed can I use a heat gun

I'd get a metal putty knife to work parallel to the substrate. A heat gun might help, but if its particle board it might hurt you by softening the glue binding the wood particles.

Only way to know is give it a try... and don't overheat it to reduce the risk of that occurring. Since a heat gun can possibly start a fire... keep an extinguisher handy

Thanks