Q:
Must fractals still be done in order?
A:
You can do higher level than you personal level, and you will level up (same goes if you do the same level as your personal)
Careful though, the reward scale with your level, so you won’t be, for example have 4 daily chests by doing 50 40 30 20 10, if your personal level is 4.
And starting to level 10, you will need agony resistance.
As long as you have enough agony resistance, you can play any level but your reward depends on your personal reward lvl.
People still play the low lvls as well, doesn’t take long to get a party, and it’s beneficial to level up by playing levels close to your personal reward lvl instead of the very high ones because, well, you need learn the content and you need AR. Few times I ran with people that grinded low lvl fracts for ages for relics, then they crafted asc gear and got AR in it, hopped to 40+ and were surprised how much harder the content is in comparison with 1-9.