Stove was cooking on one burner all of stove shut down why !

 Power stopping at the board is a very good indicator that your problem may be with in the board itself.  Have you detached and reattached all electric connections?  Sometimes with a total power failure it can be something as simple as a loose of power due to a loose harness connection.  If all your connections are good make sure you have correct power at the outlet (if you have not tried that yet).  Next take a picture with your phone of all the connections and remove the board.   Traditionally there are -2- things you can look for on the board, a burned out relay or a burn spot on the board itself.   If you smell the board Is there  a burning odor?   If you have burn spots and/or a burn odor chances are good you need to replace that board.   
 As far the original part number being substituted out to a new part number, L-G is notorious for this, I would not look at that as a sign that you have a defective part per say.   They seem to change/update to new part numbers more than most of the other brands out there, usually without releasing information to the public on why.  
 We hope this helps!