1. Nasomi specifically avoids giving QoL stuff, since many of the things that made FFXI fun were taken away when SE added those. But, we do have things like fully linked AHs, and no bazaar tax in Lower Jeuno for example, so that you don't have to bazaar outside in Rolanberry. Most 'changes' are small things like that, ones that might have an impact on the game (AH linking means all prices at all AHs end up being the same, the markets aren't isolated) but are necessary since we aren't quite as large as the top retail servers of the day. Limited level sync is another one: you can sync 10 levels. So you can't hit 75 in the dunes, but you may be able to hit the upper 20s if you really hammer it in in the dunes.
2. The Emperor and Empress bands, yes. They are enabled only during EXP events. They're the same rings you remember, nas just uses them to give incentives for EXPing on certain days. For example, Valentine's Day, Thanksgiving, Christmas, etc...
3. Yes, you need to do the quests to unlock the Advanced Jobs. That includes the quest for subjob, too. Nas is working on fully implementing ToAU and you can read more about the ToAU roadmap here:
viewtopic.php?f=16&t=77594. Very available. One of the changes to the AH was allowing for you to list 100 items, not 7 (though you can't see more than 7 in your Sales History ingame, you can see them on the website in your account page:
https://na.nasomi.com/account/login.php), so players tend to make these in bulk for gil, and compete with each other.. and, well, you know how it goes.
5. There's lots of ways to make gil, but nas is also very strict on RMT where SE tended not to be. Some prices are higher, some lower, and it varies a lot depending on the trends people set. I wrote a newbie gil guide that could help you in your very early days if you're interested:
viewtopic.php?f=6&t=4645