Did anyone knows some differences between (12 Rivets) output shaft
They have various absorber gear wheel:
ABSORBER GEAR WHEEL K1200 - 11211464947
ABSORBER GEAR WHEEL K100 - 11211461499

There are the same springs between the absorber gear wheel and idler. Idlers are the same.

Will absorber from k1200 fit to my k100 engine?

I suspect you will be one of the first to know the correct answer to this question when you have all of the pieces laid out before you. Sometimes BMW make a part number change because of an item's metallurgy, other times it is because the item is physically different though similar looking from an item from a different model. Interchangeability often simply comes from trying the various bits together until you get an idea what works.