Definitely not. Deku's character arc in the manga is centered around his growth and development as a hero. There are challenges and difficulties, but he never turns to the dark side.
Deku remains a hero in the manga. His determination and sense of justice keep him on the path of righteousness. There are no indications or plot developments suggesting he becomes a villain.
In the manga, Deku stays at UA. His journey is centered around his experiences and development within the institution. There are no plot points where he leaves UA permanently.
No way. The manga portrays their connection through mutual respect and competition in their journey to become great heroes. A kiss is not part of that narrative at all.