I purcharshed three gallons of paint with different texture where the wrong one they havent been used , just purshchsed would I be able to change it?

Depends on how much time has passed

I would call the store and ask them about their return policy and explain to them your problem.

Yes you would be able to change it, just don't take too long to change it a receipt is a plus

Not sure about custom color but worth a shot

Take them to the store.

Yes

Yes. I did that before actually. I didn't like the custom color I got so so returned it for a better color.

If you haven't used it and have a receipt they should be able to swap out for you.