OK it appears you are confused, so I will try to clear it up for ya
UMDGen is only a PC utility that allows you to rebuild PSP iSO images for use on the PSP. It uses the PARAM.SFO file contained in each game iSO to determine the Firmware Version the game uses, and reports it on the bottom of the utility (as pictured on the UMDGen site) so that users will know which version libraries are used on the title.
Currently you can only play UMD iSO images on a v1.50 PSP, and if you have a v1.51, v1.52, or v2.00 you can downgrade to a v1.50 to play them that way. Anything higher than a v2.00 (2.01+) cannot currently play them, and there is no way to downgrade those yet. Additionally, there is no known estimate when you will be able to play UMD iSOs on v2.01+ so only time will tell. If you need to know more about any of the above,
search in our
PSP Chat section as all of the info is already there.
This section is only reserved for
UMDGen questions/issues such as "rebuilding XYZ game, I need help with..." and so on.