Clementi/Tausig Gradus ad Parnassum

[bandy]

I've just started studying Tausigs selection of studies from Clementis "Gradus ad Parnassum" (found here: https://www.sheetmusicarchive.net/single_listing.cfm?composer_id=34. In the first bar of the first study, Tausig gives three alternative fingerings: 1 2 3 4 5 4 3 2, 1 2 3 4 1 4 3 2 and 1 2 1 2 1 2 1 2 1.

What is the deal with this? Is this pattern to be followed through out the whole of the study? Is the last fingering (1 2 1 2...) supposed to be played in tempo? Is that even humanly possible?

Thanks in advance.