I've published a free game with ads on google play store. https://play.google.com/store/apps/details?id=com.oxene.games.xelevation
some players suggesting to have IAP to remove ads. I would like to know whether it is possible to add IAP to a already released free game?
Based on your comment:
you can't convert free app to paid app later
In-app billing can be implemented in both paid and free apps.
I would like to know whether it is possible to add IAP to a already released free game?
Yes, it is.