Quick answers

What is Sonic the Hedgehog 3 & Knuckles about?

Sonic the Hedgehog 3 & Knuckles (or simply Sonic 3 & Knuckles or Sonic 3 Complete Edition) is a platform video game which is the result of locking-on Sonic & Knuckles with Sonic the Hedgehog 3 using the former catridge's unique "lock-on" technology. It is essentially a large combined game of its two lock-on components and contains all Zones from the said games and also contains special features unique to this game. This would have been the original Sonic the Hedgehog 3 the developers intended but time constraints by Sega resulted in the game being split into two.

When was Sonic the Hedgehog 3 & Knuckles released?

Sonic the Hedgehog 3 & Knuckles was released on 18 October 1994.

Who made Sonic the Hedgehog 3 & Knuckles?

Sonic the Hedgehog 3 & Knuckles was made by Sega Technical Institute and Sega.