Can you reverse hairline lowering?

As others have mentioned, tissue expanders can be used, but it is still possible to elevate the forehead and hairline without doing that -- you just might not be able to get a full 1.5 of 2 inches of movement like you mentioned in the question.  The way to do this is simply to excise a strip of the hear bearing scalp behind the current hairline, undermine into the forehead, release the brow attachments, and then elevate the forehead / hairline.  What I just described is a coronal browlift.  The only difference is that the incision placement would likely need to be different than the standard incision pattern based on the location of your previous hairline lowering incision and scar.

Reversing low hairline? Yes this can be done with tissue expansion but would require wearing a scarf to cover your forehead while expanding for 8-10 weeks.