Making Money with Android

Can you convert a completely free game to an IAP game?

I want to release my game for free (with a bit of ads here and there) and then if the response is good, convert it to an IAP game.

Does play store allow this?

I had read that you cannot convert a free app to a paid app.

You can’t change a free game to a paid one, but you can add IAP to your game even if you didn’t have them in the beginning.