It probably depends on the writer who is currently writing him, but chat gpt thinks he would eventually recover from decapitation or attacks that destroy his brain. I can’t remember where I got this from, but my understanding is that as long as some of his cells survive, he will regenerate. Which could rule out the surviving the sun depending on whether he’d burn up faster than he can regenerate (and assuming no new powers affect this).

It changes based on the comic book, from what Ive read. Theres comics where hes survived being beheaded and his body kept elsewhere.