Pretty much everything. Our body is just a big floppy meat suit without a brain to act as puppet master.

all voluntary and sensory abilities are controlled and/or processed by the brain, as well as certain involuntary actions like consciousness, sleep, and breathing. because of the last bit, technically everything needs the brain because breathing provides oxygen, which is needed to produce energy for all cells to function.

certain involuntary actions don't necessarily require the brain though, like the beating of your heart, which has its own electrical system that lets it keep beating without input from the brain. however, the brain does regulate and modify it when necessary, like when you're scared and your heart rate goes up. there's probably a few more that i can't think of off the top of my head, but short answer is pretty much everything.

A lot of the digestive system is also automated, although it too can be overruled by the brain.

Reflexes are controlled by local nerves and muscles. Some biochemistry is controlled by hormones made by glands, which affect how cells behave. Some is controlled only by the cells themselves.

Instincts, emotions, thoughts, memory, muscle memory, all voluntary movement is controlled by the brain.

Pretty much all of them?

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Doesn't the brain control chemicals and or have chemicals in it?

Like which ones?

Yes, as I said chemical processes governed solely by the laws of physics might still work but thats going to happen the same whether you’re alive or dead.

Doesn't the brain release chemicals to control organs? Sorry i don't understand these chemical processes your speaking about?

There aren’t really any useful ones I can think of which is probably why you can’t either, but I was trying to cover all bases so some snarky redditor wouldn’t be able to catch me out with a “well what about such-and-such”.

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All of them. The brain receives information from other parts of the body, and decides how to react.