Retin A vs Retin A Micro and hands

Could someone please tell me what the difference is between these two
products? I started about a month ago on Retin A .05%. Doing some reading
on Google Groups, I came across references to Retin A Micro. I had the
burning and peeling but it only lasted no more than two weeks tops. Seems
like others suffer much longer. I do have sensitive skin and after the
initial red/peeling, I reduced the application to every other night. Are
there different strengths of Retin A? Is the .05% a normal (average)
strength? Also, what about using it on the back of your hands? Has anyone
tried that and is it helpful?
Thanks,
Monica