How do you bypass game purchases?

I’ll apologize in advance as I’m 99% certain this topic has already been covered around here. However, I can’t seem to find it, so if someone can re-explain or point me to a post that does, I’d greatly appreciate it.

Obviously I’d like access to full versions of Ouya games I purchased back in the day, that currently only work as demos. Shadowgun comes to mind, but I know I have several others.