What's your question?
1 is an estimate; probably more than an hour and less than three
2 Doesn't mean anything likely.. It implies that John was obliged to start at least two hours ago - maybe he has a regular duty. Any context that supported this usage would have to pretty contrived. (There's a challenge. )
3 Another sort of estimate - a long time: well over an hour and a half, probably two.
Student or Learner