This really depends on the cell line. They might not like it and get stressed or die. Or they will be fine and grow "as usual" (take pictures and record growth time to get a certain confluence!). You will likely have to redisperse again after the two hours. It may even be necessary to trypsinize again if you see large cellular aggregates that won't redisperse. In any case, I would avoid this step if you can.
I would say yes as long as you leave the tube ajar, and as said above by Sven, you take care of resuspending them correctly after the 2h. But really be careful not closing the tube to much.