Yes: Classic Sonic is both a younger Sonic and from another dimension.

[Ikagura]

I know it may sound complicated but it isn't.

When Classic came to meet his Modern/Future self in Generations he learned a lot (thus leading to a new continuity that became Mania while Modern did the events of Lost World) and then when he met Modern again in the future (but further) he had new experiences that Modern actually didn't have (like the Drop Dash) because he didn't do that in his own continuity.

As a better comparison see Future Trunk and mainline/Prime Trunk from DBZ (and no, not like Silver the Hedgehog this time), Future got a different experience and life than Prime that didn't see his friends and family die. In fact he doesn't know fusion nor SSJ3 despite being still the older version of the same character.

Another exemple is Biff Tannen where in Back to the Future 2 he gives his younger self the Sport Almanach which turns him into that one rich guy (while the old Biff from 2015 vanished because of time paradox but it's another story) so basically he both existed as an older and alternative timeline version of the character.

[Mez Koo]

Lost World had a version of drop dash and he had it in Frontiers before spin dash was added.

[Crystal Sharrd]

The way I interpreted it is that the Classic Sonic from Sonic Generations is a younger Sonic from the past, while the Classic Sonic in Sonic Forces is from the alternate universe of Sonic Mania.

[Mez Koo]

Originally posted by Crystal Sharrd:

The way I interpreted it is that the Classic Sonic from Sonic Generations is a younger Sonic from the past, while the Classic Sonic in Sonic Forces is from the alternate universe of Sonic Mania.

The Sonic from Mania/Forces is the young Sonic from a timeline split because of Generations, which is actually canon and not just the "everything is canon" crap, there is a second Sonic timeline unless Sega has modern Sonic reference to Mania or Superstars at some point but Sega did canonically established a multi-verse with potentially "infinite Sonics" so we could see them keep Classic and Modern separate along two game lines now such the upcoming Superstars being its own thing.

They spelled it out 6 months ago with a Tails Tube and with hindsight this was probably the hint at the return of Classic Sonic with Superstars. https://youtu.be/CnnqXIGA_UQ?si=8mSAthHUC72BfkyW

[Ikagura]

Originally posted by Crystal Sharrd:

The way I interpreted it is that the Classic Sonic from Sonic Generations is a younger Sonic from the past, while the Classic Sonic in Sonic Forces is from the alternate universe of Sonic Mania.

And Mania is the sequel of Sonic 1, 2, 3&K (and CD) ergo it's also Classic Sonic from Generations.

[Mez Koo]

Mania comes after the originals and could certainly be called Sonic 4 if they didn't already waste that name but it's not necessarily a sequel as that would be Sonic Adventure.

[Ikagura]

Originally posted by Mez Koo:

Mania comes after the originals and could certainly be called Sonic 4 if they didn't already waste that name but it's not necessarily a sequel as that would be Sonic Adventure.

Blame the marketing team at Sega insisting to rename Sonic Mobile into Sonic 4 just to go with Generations...

[Mez Koo]

Apparently they went back on it and Mania is now part of the official main line going 3&K -> Mania -> Superstars -> Adventure so the "new" classic distinction of games are probably always going to be perpetually "before Adventure."

https://www.eurogamer.net/sonic-teams-takashi-iizuka-on-co-op-play-pixel-graphics-and-getting-momentum-right

You've previously discussed a Sonic timeline for the games and Sega has a Sonic lore team. Where does Sonic Superstars sit on the timeline? How does it connect to other games in the series?

Iizuka: The Classic series began with Sonic 1 in 1991, and Sonic Adventure marked the switch to the Modern series in 1998. So in terms of the Sonic timeline, Sonic Superstars occurs after Sonic Mania and before Sonic Adventure. Whenever we develop a new game, we always make sure the story fits with the lore.