1. that would make these sequels to SM
3. that doesn't even sound reputable
4. possible... but it depends on what happens in the story
5. Lillie is the champion!
I saw this posted either on Twitter or reddit. It gives me hope that USUM are sequels, but I'm going to consider it fake until proven otherwise.
1. Not necessarily. It could just mean Elio/Selene moving to Alola was the linchpin that kicked off Sun/Moon in the first place, so if this is true, the story is most likely a "what-if" situation. Don't forget one of Pikachu's Dex entries said that the plan to make the Pikachu Power Plant was only just announced (by comparison, the first time the Rotomdex saw Silvally was under Gladion's ownership, and he's implied to have given the species its name), so the entries likely by and large go by a mix of programmed data and whatever Rotom itself learned from Kukui.
2. Meh. It's probably gonna be Kukui, or even Hau.
3. It's most likely a much more dangerous Team Skull still answering to Aether.
4. I'd kind of prefer them to be forms of Necrozma, since them being Solgaleo/Lunala's forms would mean the former is the only third member that didn't somehow improve after the initial two versions. Though it would make sense if Necrozma is a dead Cosmoem (spoiler alert: Nebby dies), or because of Prism Armor.
5. I do love me some good Ascended Fanon.