Student or Learner
" Hi! Long tmie no see! Where hav you been? I don't even remember when I last saw you!"
I would say " I last saw you". What about " I saw you last"? Any differece?
They sound the same to me in terms of naturalness and meaning.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.