Is Knuckles the Echidna in Sonic the Hedgehog 2 on Steam?

No. Knuckles the Echidna in Sonic the Hedgehog 2 is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.

What platforms is Knuckles the Echidna in Sonic the Hedgehog 2 on?

Knuckles the Echidna in Sonic the Hedgehog 2 is available on Sega Mega Drive/Genesis.

When did Knuckles the Echidna in Sonic the Hedgehog 2 release?

Knuckles the Echidna in Sonic the Hedgehog 2 was first released on October 18, 1994.

Knuckles the Echidna in Sonic the Hedgehog 2

Oct 18, 1994PlatformSega Mega Drive/Genesis

Knuckles the Echidna in Sonic the Hedgehog 2 — frequently asked questions

Is Knuckles the Echidna in Sonic the Hedgehog 2 on Steam?: No. Knuckles the Echidna in Sonic the Hedgehog 2 is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.
What platforms is Knuckles the Echidna in Sonic the Hedgehog 2 on?: Knuckles the Echidna in Sonic the Hedgehog 2 is available on Sega Mega Drive/Genesis.
When did Knuckles the Echidna in Sonic the Hedgehog 2 release?: Knuckles the Echidna in Sonic the Hedgehog 2 was first released on October 18, 1994.

About Knuckles the Echidna in Sonic the Hedgehog 2

Knuckles the Echidna in Sonic the Hedgehog 2 (or simply Knuckles in Sonic 2) is a platform video game which is the result of locking-on Sonic & Knuckles with Sonic the Hedgehog 2 using the former cartridge's unique "lock-on" technology. As the name suggests, this game is essentially identical to Sonic the Hedgehog 2 with the exception of Knuckles the Echidna starring as the main playable character, and Sonic the Hedgehog and Miles "Tails" Prower are not playable in the game.

Summary via IGDB.

Knuckles the Echidna in Sonic the Hedgehog 2 on Wikipedia

Sonic the Hedgehog 2 is a 1992 platform game developed by Sega Technical Institute (STI) for the Sega Genesis. Players control Sonic as he attempts to stop Doctor Robotnik from stealing the Chaos Emeralds to power his space station, the Death Egg. Like the first Sonic the Hedgehog (1991), players traverse side-scrolling levels at high speeds while collecting rings, defeating enemies, and fighting bosses. Sonic 2 introduces Sonic's sidekick Miles "Tails" Prower and features faster gameplay, larger levels, a multiplayer mode, and special stages featuring pre-rendered 3D graphics.

Source: Wikipedia (text under CC BY-SA 4.0).