Well, others have basically said their counterarguments, but I have more counterarguments but will note some portains I might agree with even if those aren't the most relevant.
I disagree on the Solaris part. Well Solaris clearly scales to the entire cosmology of the Sonic multiverse given his "Destroy all existence" statement. But Sonic does still scale in terms of AP, even an anchored state Solaris was stated to be able to "Consume dimensions" for lunch. Which is clearly tier 2 regardless of whether it be one by one or all at once. Although, destroying all existence and the fact that multiple timelines appeared to be effected at once would imply it is indeed Low Multiversal. Also, while it is true that Solaris has a weakpoint, even that weakpoint is still durable to the point where only attacks that strike it in all time periods at once is required to take him out. Also, it's specifically stated Sonic is the strongest he's ever been, and that he reached the level of Solaris in the canon statements; so I think that should speak for itself AP wise. Also, Solaris is like the only final boss who actually depletes Sonic's HP, so the game mechanics statements actually doesn't work. As most other bosses were implied to be stomped by Super Sonic and he won without a scratch.
Alf Layla wa-Layla has statements about warping the entire space-time continuum and having the power to destroy it all. He seems legit Low 2-C and we can't really divide Low 2-C feats by timeframe like we can with 3-A feats. And he literally devourers the timeline iirc; much like what Solaris does. And you're right Darkspine isn't Super Sonic and is in a class of his own, but he should still be allowed to scale from his own feat. As much as Super Sonic even in his variable showings may scale from any of his feats. So I disagree with that one too.
The only one I sort of agree is iffy is Egg Wizard example; but for other reasons. But I want to wait for the thread to be made because much like the stabilization feats standards, there's going to be one for merging two or more universes. The feat of the Power of the Stars itself is clearly 2-C, but it may not scale to his striking strength or durability. While there is a statement about being superior to the "Combined might of Chaos Emeralds and Sol Emeralds", that's not always consistent. It is a sequal to Sonic Rush, thus can be compared to the combined Emeralds own 2-C feat, and while it has been made after Sonic 2006; Sonic's chronology is kinda nonlinear and simply being made first doesn't always mean it takes place before or after it. But I can agree that may be evidence of Egg Wizard being 2-C physically. Sonic would still be 2-C at his peak from the Solaris example though. And unlike Solaris, Egg Wizard was a another boss fight were Sonic and Blaze were portrayed as a stone walls. So Egg Wizard is 2-C via Power of the Stars, but I'll wait for the universe merging revisions before debating the physical stats.
That's all I got for now.