Should the order of RobTop's levels be changed?

no because then the whole concept of “introducing new gameplay features one at a time” will be completely ruined

no because the updates are different and it will ruin the difference in looks

imagine this :
after xstep that has a simple decoration, continues with geometrical dominator which has more complex gimmicks

If we'd judge by difficulty, I'd go with that:

1. Back On Track: it's considered the easiest level by many people and I kinda agree with that. It has more "auto" parts and more single or double spike jumps. Has no triple spikes compared to Stereo Madness.
2. Stereo Madness: mostly because of the two triple spikes. Also the last coin is quite hard for beginners.
3. Polargeist: honestly similar in difficulty but the coins are a little more tricky.
4. Dry Out: first upside-down mode level, may be tricky for beginners.
5. Base After Base: Same as above, slightly harder upside-down part.
6. Can't Let Go: only the upside-down part is kind of tricky but the rest of the level is easy.
7. Jumper: has more than one upside-down segment, so it might be a small problem for beginners. Still it's quite easy and I don't really think it should have the "harder" face.
8. Blast Processing: pretty easy level, however getting used to the wave might take some time. Other than that it's really straightforward.
9. Cycles: it has some triple spikes at the beginninig and the last ball has a few tighter timings, so it may be hard for some people.
10. Time Machine: the last 20% is kind of hard. I used to have a lot of trouble when I was a newbie.
11. xStep: pretty straightforward level but it has a few fakes here and there. Overall not too bad. A typical harder level IMO, not really insane these days.
12. Electroman Adventures: not too bad. The transitions may take a while to get used to but overall the level isn't really difficult. A typical harder IMO.
13. ToE: I mostly put this there because of the coins. They're more difficult, especially the middle one which is nuts for beginners. The rest is a typical harder rated level.
14. Geometrical Dominator: a lot of people have trouble with the memorization part. Even though most of it is well synced with the music, you have barely any reaction time so you have to memorize everything. Otherwise it's a typical harder level.
15. Fingerdash: not too difficult but I'd put it there because the spider is a very sensitive gamemode and it takes some time to get used to it. The last coin may be difficult for people who aren't very good at wave.
16. Clutterfunk: this is the first level where you have to click a lot and you have less reaction time than usually. It may take some time to get used to the mini cube segments and to the last cube section.
17. Hexagon Force: duals may be confusing for people at first, that's why it's so high. To be honest, only the first dual was confusing for me because it's not symmetrical. The rest is which doesn't make it too bad.
18. Electrodynamix: pretty much the hardest insane rated official level. It's fast-paced and has quite difficult ship parts. I'm suprised it wasn't rated demon at the time it was released. Back then a lot of easier levels were demons.
19. Clubstep: most of the level is kinda easy but the last 2-3 ships can be problematic. UFO timings aren't too bad but it takes a while to get used.
20. ToE II: slightly harder than Clubstep IMO. It has more memorization, more pattern clicks and more gamemodes to get used to. The coins are also slightly harder than in Clubstep IMO.
21. Deadlocked: obviously the hardest official level. This won't be too bad if not the wave parts which are pretty hard. There are also a few memory parts (like the ship maze section).

But I guess levels are like that because of the updates. Currently they're shown in the order of the updates. Maybe a way to sort these levels would be good?

I think the idea alone in the game would be beneficial, however if there was a switching option to choose between when the levels came out and the difficulty from easiest to hardest would be pretty cool.

Basically what everyone said. I like that they introduce new ideas one by one. For example, back on track introduces orbs, hexagon force introduces duals, etc.

no as the current version is represented by updates i believe it should stay the way it is now because i like how it introduces certain objects in certain levels