No, that's not where the Tasmanian Sword is; you can get that sword as a lion (or mouse, but lion is easier).
Then I have no idea where it is. And anyway, to reach the boss I have to do all that crap first, and I feel absolutely not compelled to do so. :P
The Tasmanian Sword is in the underground area, in a dead end shortly before the temple. (It's in a hidden shop.)
Once you get the sword, you can just quit from the menu and the game will automatically save, or you could just use the sword to turn into a bird (assuming you've already unlocked that form normally) and use the same door you used after you first killed the boss.