sbm12 is correct. You need to find out the "region" in which DXB is situated for a Skyteam RTW paid ticket. Within a region (normally a continent) you can backtrack as much as you like. I have flown CDG-SFO-IAH-LAX then onwards to NRT, then NRT-(MXP)-LHR-FCO-ATH-CDG, thus backtracking significantly in both North America and Europe. But I had to be careful that in flying from NRT to LHR (where I then 'stayed' several months -coming back to Paris and returning to London to take up the trip again by train) that I didn't connect via CDG. That would have brought the trip to an end.