Here is an overview of the collection, via Sega:

About

Sonic Origins is an all-new multi-game collection reintroducing the fan-favorite 2D Sonic titles that were originally released on the SEGA Genesis / Mega Drive platform—Sonic The Hedgehog, Sonic The Hedgehog 2, Sonic 3 & Knuckles, and Sonic CD, digitally remastered for current generation platforms. Developed by SEGA, Sonic Origins delivers the legendary, non-stop Sonic action found in the original games, while providing a fresh twist with remastered visuals, added features, new content and modes, and more.

In Sonic Origins, players will join Sonic, Tails, and Knuckles to race at lightning speeds across remastered versions of iconic levels like the Green Hill Zone and Chemical Plant Zone, for a classic supersonic experience modernized for current generation platforms. Players can switch between the Classic or Anniversary Modes to spin through loop-de-loops and score rings on a mission to save the world from the evil Dr. Eggman. With Sonic Origins, Sonic fans new and returning can celebrate the classic Sonic games that built the legendary franchise into what it is today. With new remastered visuals, characters, game modes, game zones, and more, Sonic Origins brings the best of the original Sonic titles to the modern day.

Key Features

• Classic Mode – Go old school with the Classic Mode and experience the multi-game collection of legacy Sonic games in their retro form with classic challenges. This mode features the original game presentation and will play in the classic finite live and game over style.
• Anniversary Mode – The Anniversary Mode provides a full screen display and offers players an infinite number of lives to keep the fun going without any game overs.
• Missions, Medallions, and Museum – Put your skills to the test and earn medallions by competing for various missions throughout the games. Players can spend medallions to unlock new content from the vault, try the Special Stage and more.
• Better Than Ever – Reset, reloaded, and remastered—Sonic Origins is playable on PlayStation 5, PlayStation 4, Xbox Series X|S, Xbox One, the Nintendo Switch family of systems, and PC with an all-new visual presentation, animation, and enhancements for the current generation. Experience the excitement as Sonic, Tails, and Knuckles.

Watch the trailer below (from 1:20 to 2:55).