I progressed through level 21 and I wiped my harddrive. Is there a way of skip to a desired level so I dont have to play the levels I already beat?
None that I know. It is cookie based, since there is no login to play Untrusted.
Your saves across levels are not saved, but your successful answer to move to the next level is saved at Gist Github. You can try searching for your answers there IMO. With luck you might find your pages with your past solutions.
But on a personal note, you can remember your solutions and try again from start. It is a fun game. Maybe this time around you can do some things differently.