The mysterious machines aren't important for the story as for now, maybe they will have something to do with the story in the future, the locked doors have a number over them, at some point in the game you will get the key card to unlock it, and the cheat codes have you need to do something in specific to unlock them in their description it says how to, you can only have three activated at the same time.
Those technically can't be open yet but I discovered a bug, as you progress on the game you will find two power ups for a changed attack, the second one even makes you shine yellow, if you charge it to the maximum with the pup form and bark with the door it will disappear.
no
I think theoretically if you were absolutely cracked? Fight is extremely annoying thanks to the conveyor belt, but is winnable (at least with near max gear).
