I have 2 Craftsman 1/2HP openers, same model # 102-1499a but 4 years apart (2005 VS. 2009)

I installed new unit and programmed remotes & keypad w/o difficulty.

When I tried to link the older remotes to the new unit, and vice-versa, no luck.

1) Is there that much diff between the units?

2) Is there any way to get the remotes to work accross both Openers?

3) Will a "plug-in receiver" work?

Please help . . .