Never thought of that. This question cleared my doubts.
Good One!

Put the subquery into temporary table and then join the temporary table with update statement. Do the same for both update statements.
 SELECT TOP (@MaxRows) OrderId
 INTO #TempOrders

good question

I think below URL will suffice your curiosity

https://technet.microsoft.com/en-us/library/cc298801.aspx

:-):-):-)

Rohit Kumar