Playing the 2.1 i found some bugs:
-The image of the Mdactyl in sand mode has a color palette glitch
-The image of the horse in arena mode uses the old design.
-The sperm minigame usually gets stuck and no sperm appear. At first they come out in rounds of 2 or 3 and then they don't come out anymore or you have to wait a long time.
(You could make the sperms appear in hordes to destroy so you can advance to the final boss).
Suggestions:
Since some of the npc animations have been improved, the enemies sprites of the stage 1 could also be improved a bit (an example would be the tentacle trap that doesn't mix well with the new level 1 floor).