>>25772
>Are the stories mentioned here from Fighters or some other part of the franchise or are they made up?
They're from other issues of the IDW comic. I don't recall precisely which ones, but they're specifically ones that feature the "Classic" characters. So you can look those up.
Also this means that they're treating the "Classic" stuff as just the past of the main timeline, rather than an alternate timeline. Of course, in one way, that makes the most sense. In a more pedantic, autistic way, it doesn't, because Modern Sonic doesn't remember fighting the Time Eater in Sonic 1 (as happened in Generations, but not in Sonic 1), and he didn't meet Tails while fighting the Time Eater with his future self, and he didn't get warped to the future/alt future again and experience Classic Sonic's version of Forces, which means he didn't experience Mania, since Mania connects directly to Forces, both regular Mania and Encore Mode.
Of course, that's autistic, and obviously "Classic Sonic" stories should be treated the same as the past of Modern Sonic. But this is technically the first time it's been confirmed that the Hard Boiled Heavies exist in the main timeline, which means something akin to Mania happened in the past of the Modern timeline. But it can't be Mania exactly, because Forces takes place in the middle of Mania, between regular mode and Encore Mode. Unless we say Modern Sonic actually did experience Forces from Classic's POV as well, and just never mentioned it. It would be slightly different since Classic remembers meeting the Modern characters before, and Modern definitely never did Generations from Classic's POV because Classic's POV of that means he experiences Sonic 1 and meeting Tails differently than happened in the actual games. But uh... I guess we should assume as much of Classic happened in Modern as makes sense, with as few changes to the "Classic timeline" we see as possible.
And to be clear, the "Classic timeline" is actually not the old games. The old games are the Modern timeline, however, we are clearly meant to assume (almost) all the old games also happened in the Classic Timeline, but Sonic 1 (specifically the part of Sonic 1 where you complete Green Hill and the Time Eater doesn't show up) and part of the backstory to Sonic 2 (meeting Tails) would be slightly different, because of things that happen in Generations. But I guess we're supposed to assume that aside from those specific differences, everything else happened as closely as possible to the games, even if not exactly.
>In the first game there are only 6.
The seventh was found on Westside Island, from Sonic 2, which happens to be the original home of the Emeralds, AKA where the Echidnas lived, AKA the island where the Mystic Ruins and Station Square are. Note that the other games which take place before Sonic 2, like Sonic 1 8-bit and Tails Adventures, also only have six chaos emeralds. (Sonic 2 8-bit also arguably takes place before Sonic 2 16-bit, as well. So does Sonic & Tails, AKA Sonic Chaos, as well as Sonic Drift and some other games which don't have much story or don't feature the Chaos Emeralds at all.) So Sonic 2 retconned the number to be 7. Note that people use the word "retcon" to mean "ignore previous continuity," but that isn't what it means, it means new info was revealed, so the old stories are canon, but now you learned new context. There was an extra emerald they didn't know about before, and it was discovered in Sonic 2.
However, Sonic & Tails 2, AKA Sonic Triple Trouble, also only has six chaos emeralds. So does Sonic Drift 2. I guess there we can assume Eggman just wasn't going for the seventh one. He got lazy or impatient. Sonic Blast only features one chaos emerald that gets broken into pieces. The others aren't part of that story. Sonic Spinball features a ton of Chaos Emeralds, but that game is arguably not even canon because it features cameos from characters from the cartoons and seems to take place in the SatAM continuity.
But Sonic the Fighters actually does have eight chaos emeralds. The immediate fan reaction would just be to pretend one of them (presumably the one Knuckles has) is actually the Master Emerald, but the game never says that, and no other later piece of media has gone back and said that was the case in Fighters. It's a mistake that's never been addressed, but given Bean and Bark are exclusive to that game (as far as Sonic game appearances go) and Fang is also in that game, this eighth chaos emerald is likely primarily a reference to Fighters, but with other references thrown in as well.