Maybe Raja's move was part of the AMD Intel GPU deal, as could be some undisclosed fees for use AMD graphics tech for use at Intel. That could mean Raja is there to lead a close integration of the tech bases.
This is unlikely, no company would voluntarily hand over their top talent especially to their rivals. Even with the new deal in place Intel AMD are very much rivals.
Normally yes, but companies also shy away from a high potential to get into IP fights about patents and trade secrets.