I'm considering buying an Y1

I'm thinking about installing Rockbox in it and changing the sd card to a bigger/better one.

But first, I have a few questions:

1. Is the OS installed on the sd card or the device itself?

2. I know that the default firmware doesn't detect more than the default storage (yet it is able to display the correct amount of storage left and read music without issues). Yet, with rockbox, would the storage amount be read correctly?

3. Should the sd card have a specific format? (ex. FAT32)

4. What about battery life? I've seen reviews but I wanna listen to people who use this device regularly

5. Is the Y1 durable? I'm thinking of keeping it in a pouch and put a screen protector (I'll have to cut, sand and polish it from another "normal" screen protector)

6. Any issues with rockbox themes?

7. What bugs/known issues I might encounter? And how do I fix them?

Thank y'all in advance :)