Does "contribute on" make sense here? "Kevin was contributed a lot on the pitch presentation yesterday"Does "contribute to" and "contribute on" mean differently?

Does "happen to know" mean "just know" ? or it has other meaning as well?

What does "stuck" mean in this sentence What does "stuck" mean in this sentence : He stuck his hand through the bars. "Congratulations," he said. ----from "The Kite Runner"

Does "... is impossible not to watch" means "... can't be avoided to watch" or something else?