there isn't an update for sx cause the team behind it were arrested and it was closed source. so since it was closed source, no one wants to go through the hassle to try to reverse engineer it.
as for patching games for lower firmware, that only works to a point. games that use newer sdk, may require certain functions that are only available in those newer sdk. so when patching it to work on lower firmware can cause the game to crash since it cant use those functions.