Short answers, pulled from the story.
The Variable Assist allows a player to summon their off-screen partner to perform a special move without switching characters. This feature expanded the role of secondary characters and opened new possibilities for combos during battle.
The PlayStation port released in February 1999 faced severe hardware constraints compared to the Sega Saturn version. Limited RAM capacity forced developers to remove the tag team format entirely from the console release.
Norimaro appeared exclusively in the Japanese arcade and console versions of the game as an original character created by Japanese comedian Noritake Kinashi. Licensing issues from Marvel prevented his inclusion in international releases since he did not align with their brand image.
Limited RAM capacity on the PlayStation forced developers to remove the tag team format entirely from the console release. The system instead switched to the traditional round format used in other fighting game series like Street Fighter.
Only Cyclops and Wolverine remained from the original mutant roster while most X-Men characters were replaced with heroes from other Marvel properties. Characters such as Dan and Sakura entered the fray to replace Cammy and Charlie.