Questions re microSD cards & SSDs

Sending ths out again because I haven’t had any answers! I use a microSD card for booting, but a SSD for everything else. I have a couple of questions:

1a) Do updates change what’s on the microSD or is it stable?
1b) Am I right assuming that if updates do alter the microSD then that’s the only time it’s written to?
2) If the microSD card has been corrupted, can I just burn a new one & replace it without worrying about anything else?
3) Is it possible to move the boot image to the SSD while leaving all the data on the SSD intact?

Maybe try ask a better question! I would for example definitely include the hardware, architecture and OS you are using in your post :wink: