I don't know how useful it will be but maybe it helps in level 5.

Saving and loading the game directly after getting a core or the central unit let's you warp to touryst island. One can see it at about 45:27 For the route i would change jazz club for football minigame.

So the game is loading the last save that was done. With the possibility to save manually you can restart at the excact position where you saved. That means if you die you start with three hearts again and with that you could ignore the cold and run till you have half an heart and then save. With this you can skip searching and cooking chillys and other stuff. Sadly it isn't working for climbing and swimming so far. It skipped the flying session of naydir the dragon after destroying one of the eyes by save and die. Maybe it works for other bosses to. I hope this helps :3