Reactpsn is like software that will enable you to play certain games. All ps3's can play ps1 games so I'm not sure what you were asking about ps1/ps2 games.
Rebug is classified as firmware I think. It is like the operational system of your ps3.
To play ps2 games your system needs to be backwards compatble or you need to have cobra dongle I believe.
If I'm wrong someone please correct me