Sonic & Knuckles + Sonic the Hedgehog 3 (World) ROM

For some people, Sonic 3 and Sonic & Knuckles are considered like separate games, however, the truth that lies beyond is greater that anyone could expect. Due to time constraints and cartridge ROM size limitations, a bigger game had to be divided. The finalized view of one game, as the producers and creators wanted is only attainable in one certain way.
Enter Sonic 3 & Knuckles, a game that can be "created" only by pushing Sonic 3 on the Lock-on cart connector on top of Sonic and Knuckles.
Considered to be the greatest Sonic game ever, it is long, entertaining and definitely awesome. In a nutshell, you'll get to play the levels of Sonic 3 followed by the levels of Sonic & Knuckles with any of our heroes: Sonic, Tails or Knuckles, on a 13-zone-long game, together with 14 special stages, 7 for each Chaos Emerald and another 7 for each Super Emerald, altogether with a faceoff against Robotnik in his Death Egg, once and for all on the Classic Sonic series.
With the regular emeralds you turn into Super Sonic or Super Knuckles, but with the Super Emeralds, you can turn into Hyper Sonic (even faster than before), Super Tails (his first super transformation for the first time ever) or Hyper Knuckles (stronger than before). Finish the whole game with all emeralds and you'll complete the game.
Added to the convenience of playing thru the whole game, the save state feature of Sonic 3 works perfectly, so you can have a well deserved rest in the middle of the game. The save game screen will show you which zone are you in, and how many emeralds you have in your inventory.
There is definite evidence that this whole game was going to be released as Sonic the Hedgehog 3 Limited Edition, but it didn't went as planned.
All in all, if you want to play the definite version of Sonic 3 with the added contents of Sonic and Knuckles, you have to play through this one particular version. It's a must for every Sonic fan, and every classic gamer.

Sonic 3 and Knuckles. To most people this is the greatest Sonic game of all time. If you are a fan Sonic then you will love this game. Even if you have never played sonic you can still enjoy this work of art. The graphics are some of the best that the genesis can offer. The music is video game perfection. So much catchy level music. The gameplay is simple. Just go left spindash and jump. You can also try and find the 7 chaos and super emeralds. If you do you can get super sonic and hyper sonic. This is not a difficult game, but is fun nonetheless. If you are a gamer you will love this game.

Sonic & Knuckles + Sonic the Hedgehog 3 or for short Sonic the Hedgehog 3 & Knuckles, just like Sonic 3 but got Knuckles in it.
There are some secrets that you can unlock like:

Super / Giant Emeralds
Hyper Sonic
Stage Select Screen (Easier than the normal Sonic the Hedgehog 3)
and etc.

that's all. >_<