Can I update from 5.3.9 to 5.9.6.1

I have a Kindle Paperwhite. I don't know what variety but it's the one with
the word "Kindle" across the back.
It's running on firmware 5.3.9 and the serial number starts with "B024".

Years ago I used a jailbreak on it purely so I could use my own fonts as
I found the supplied fonts were too pale for me.

Now the latest firmware, 5.9.6.1, allows you use use your own fonts
I would like to update to that, but I have a few questions.

1. Can this latest firmware, 5.9.6.1, be loaded to my particular Kindle?
2. Can I go straight from 5.3.9 to 5.9.6.1 in one go?
3. Do I have to remove files like USE_ALT_FONTS and
directories fonts and update.bin.tmp.partial which I think were
part of the jailbreak?
4. Is there anything else I should be aware of?
5. Finally, my device is unregistered, can I keep it that way?
I never use Amazon for books.

Thank you very much for your expertise,