Game Access in Developer Product Form?

Would it be possible to tell the system 'if player.purchased.asset = --Developer Product ID here' because they do have an ID so I think it's possible but I don't know, and as they are supposed to be bought more than once, would it still work as permanent? and if I removed it from my game, and people had purchased the Game Access in the Past could I still use the 'if line' from above to award players? and if you could do all that, then how? and another thing, for the Blank screen, do I use the line from above and say 'then script.Parent.Visible = false' would that work? and of course I have more questions it's just that I can't remember them. Also if I wanted to make a Rent function, would I do the line from above and say 'then script.Parent.Visible = false, wait(24 hours), (tell the system to count even if player offline), then tell do visible = false' etc...