Decent Sprite animation, but I would recommend using different sprites or creating custom sprites. Maybe even custom scenes such as different over the shoulder shots and a little cleanup since the first few seconds, Sonic jumped from one spot and warped about 5 inches closer trying to use Chaos Control... and failing.
If your looking for different software to accomplish these task's; I can point you in the right direction. I'm going to wager you probably don't have much $$$; There is an animation software about $5-$20 Called Anime Studio [Debut] Published by a company called Micro Smith. It isn't perfect; since you can't separate the scene's easily or categorize the piece's to scene's; However to do animation like this, you may get better use out of it.
Second piece of software I'm going to recommend for sprite work is Aseprite; it's one of the best spriting tools on the internet. There are probably better ones, though I prefer this one for it's file formats and ease of animation, especially animation I can export as a large sprite sheet to dump into a game and use it as an art graphic or as a Gif for fun.
Next; I don't wanna break your heart over this lad, but Flash is now the way of the Doo-Doo, it has become the Radits of the Internet among web designers, It is dying of Dysentery, it has become the butt end of Joker's Jokes, It is currently set on fire and we're waiting for the fire to die out.... My jokes aside, Flash will no longer be supported; new grounds stopped accepting Flash products since Adobe claimed they we're permanently no longer supporting it since you can now do everything else in.... well, take your pick; HTML5, CSS3, Javascript and so on. Flask is seeing development which is a web app running in Python and there's another application where folks using the .net structure will be able to write web page apps, animations, and even games in C# using 'Blazor.'