It is important to note that each game has checks as the ps2 system did. If you were running the game on a cd but it was a dvdr the game would not work unless your properly hex edited the game. The same is similair with the UMD. Once we know the key to that we can properly make a game run solely from the memory stick, game that use a dev kit are already made for the memory stick but games specifically made for the UMD (licenced by $ony) have this protection in them.
Find out the pattern and then the game will slowly start working. You just need to know what 2 look for.