for slap: I'd go back to biblical times, I'd slap joseph for beliving that his wife imaculatly conceived a child... then hang around for 30years to see If i'm right or wrong.
Kiss - If i was getting the choice of going anywhere back in time, to kiss anyone, I'd prob just pick a week and knock on beyonce knowles door!
and with regards to keeping alive... I dont think I could or would. who would you pick? like someone else said. everyone has their time.