This is the Hidden Palace Zone Good Future, it is far more finished in released versions than in the screenshot.
This is one of the glowing orbs from the Good Future.
A green orb high up on a cliff.
To access Hidden Palace Zone, you need to build a portal out of polished granite, and then ignite it with the Emerald Shard.
Not all of them are from Sonic 2's Hidden Palace Zone. Some from other classic Sonic games are there for variety's sake.
A glowing orb next to the water at the bottom of the cave.
You can see the blue glowing orbs, the palace floor, and the water at the bottom of the cave.
The palace platform, visible higher up away from the water.
Now including tool sets!