Still haven't beaten Bubble Bobble after about 25 years (or so...)

Bubble Bobble features three endings: the bad ending, the good ending and the true ending. They are unlocked depending on how you play the game.

Bad Ending
If the game is beaten in single player, Betty is rescued from a bubble, but not Patty. The game tells you to "Never forget your friend!" and sends you back to the start of the game.

Good Ending
If the game is beaten in multiplayer, Betty and Patty are rescued, but the game informs you you have not reached the true ending. It displays a code to input at the title screen that unlocks Super Mode, which you must beat to reach the true ending.

True Ending
If the game is beaten in Super Mode, Betty and Patty are freed. A large Bubble Dragon drops down and transforms into Bub and Bob's parents. The game then plays a message:
CONGRATULATIONS!

YOU COULD HELP YOUR FATHER &

MOTHER! THEY WERE CONTROLLED

BY SOMEONE. WHO IS HE? NO ONE

KNOWS OF IT! THE TRUTH IS IN

THE DARKNESS FOREVER...

No there´s no need for an extra item, I finished the game as well and a full replay with actual ending is online on my youtube channel.

At player select screen you use the following code to enable Super bubble bobble mode:
Up, Left, Down, Left, Down, Up, Up, Left

Make sure, you end the game as well with 2 players!
https://www.youtube.com/watch?v=4rx3D46qDRY

I seem to remember someone doing an enhancement patch for this game..

What does it do, and is it still available??

And no, I haven't beaten it either

Can someone test on a Panasonic MSX2+ with 5.14Mhz mode?

Yes but I would like to know if the sound is the same on a real MSX2+.