Reloading un-beat Unity, and let me go find ??? Then when I lost the fight the first time suddenly I got an ending :/ I totally coulda beaten them, though; they honestly seemed way easier than Unity it would just take a couple tries.
Congrats on beating Unity and sorry for the issue! Sadly that's a bug that I only discovered after the submission period, where the boss doesn't despawn correctly after beating all the sub-bosses. I will definitely be uploading a fix for that first thing after the voting period ends on April 6th.
As for ???, you should be able to press Esc and load the game during the final cutscene, or just close and reopen the whole game and it should put you back before ???. (I should probably make it so after a few attempts, it stops putting you in the ending and just loads the game automatically.)
Just to save you some frustration, there's sadly also a bug with ??? where a lingering hitbox might prevent you from finishing the fight at the end (but the fight itself functions correctly).
Even if it did count, beating Unity doesn't do anything right now besides opening a shortcut back to the starting room so you don't have to go through the spikes again. Beating ??? only changes one minor line of dialogue in the ending.
Again, apologies for the game being so unfinished, and big congrats on beating Unity, I definitely tried my best to make the boss hard! And if you choose to keep trying to beat ???, good luck!