2. Yes. There is a very small chance that it might get bricked however if this does happen you can just restore to a recent backup and everything will be fine. It's a minor inconvenience at most.
3. Yes, it's super easy to go back to normal. You can either wait until Apple release an update and then install it as usual which will remove the jailbreak, or as before you can restore to a recent backup which will also remove the jailbreak.
I understand I'll have to jailbreak my phone to access this, but is there a way to view a list of networks my iPhone has remembered and get info on the date they were last accessed?
I know there are some Cydia apps that allow you to view all the stored passwords for previously accessed networks but I'm also interested in seeing the date they were last accessed - dunno if that's possible or not?
I have no idea about that if I'm honest but I imagine there will be a tweak for it if you look around. The jailbreak subreddit is a good place to look for tweaks, and you could ask someone on there who knows a lot more about this sort of stuff than I do.