so then, no, there is not really way to "go back". You can however, drag them in the tree to be adjacent with no effect on the outcome as far as the solid shape goes.
Not sure. Here are my Cliff's notes:
1. If you are doing straight-brake sheet metal or machined parts, I would do Synchronous straight up.
2. If you are doing plastic/cast parts, I would do the principal design in Synchronous and then do the draft/fillet treatments in Ordered (hybrid tree). You can also use this approach with straight-brake parts that have a cut that wraps a bend, say.
3. If you are doing surfacing, I would do the main sketches in Synchronous, where you can take big advantage of the lack of order, and do the surfaces themselves in Ordered.
Happy to advise on your particular situation, but that is the broad brush strokes...