Is it kool for a bowler to bowl off and leg spin in the same game?

I'd say that's fine! Surely it's an art to be able to bowl good off spin and leg spin. Spinners now have many variations so switching between is just like another variation. I've seen a couple of bowlers bowl off spin for left handers and leg spin for right handers

It's not even an "issue".

It is perfectly within the laws for a bowler to do that , although in reality the skills and techniques involved are very different and hardly any bowler is capable of bowling BOTH genuine off and leg spin effectively.

ya why not? it will try to confuse batsman and helps for getting the stumps

Anyone can do that but if he fails to generate consistent line, then it will be no more kool.