So, firstly, may I suggest you check youtube for one of the now many 'Adventures of Torso' type videos done in Kenshi.

But as far as keeping a 'minimum viable' human actually alive?

You could remove limbs, but you would still have to have a method for them to eat and urinate and deficate.

You... almost certainly could not remove all skin and keep someone alive for very long.

For starters, they'd bleed to death. Secondly, the pain of existing without skin would probably literally kill them or drive them to try to kill themselves. Thirdly: Skin prevents infections, you'd have to keep them in basically a totally hermetically sealed room or container.

Bones? A de-boned human?

Well there's almost certainly not a way to remove all of your spinal bones and skull without causing death or immensely serious paralysis and/or brain damage.

Sure you could remain alive without all your limbs if you have caretakers, you can survive without your lower jaw as well... You can maybe? survive with the loss of a certain high percentage of your ribcage, but probably not with the entirety of it and your sternum removed.

Organs? Well, brain, heart and liver are almost certainly mandatory.

Though you can remove portions of your liver and it can still function and regrow to some extent...

...and portions of your brain... though you'll lose cognitive abilities, memories and basically become braindead but still technically alive at some point.

Assuming we are just removing things and maybe hooking you up to various kinds if life support tubes and not replacing organs with some kind of mechanical or genetically engineered equivalent:

I think you can survive without any kidneys if you are constantly on dialysis, but its far better to have at least one.

Similarly: Lungs, you need at least one.

You can have your stomach and intestines and bladder partially removed or reshaped, but not entirely.

You can survive without eyes... and a gallbladder and a thymus and a spleen and an appendix and your tonsils... and your adenoids, and your sex organs, but you're gonna need a great deal of monitoring and bloodwork and hormone balancing and what not.