Primary stats are capped at 100.
You can cheat as much as you wish in single player games, assuming you are not bothered by the possibility of making things too easy. The only legal issue would be if you needed to bypass copy protection to cheat, or something. Multi-player games have a section in the end user license agreement about not cheating or using unauthorized third party programs so the developer/publisher can take punitive action against those caught doing anything they don't like.
