
!cheats for blueMSX :gulkave
!(c) 2005 Albert Beevendorp and (c) 2005 Patrick van Arkel
!(c) 2006 Benoît Delvaux
0,58029,255,0,energy
0,58023,8,0,weapon (0-16)
0,58053,6,0,lives
As mars2000you, I have already made all these steps ... but it's not the good answer !!!
find out that completing the game unlocks hard mode?
A little tip : at the end of the 'normal' game, there's an important message !
Just press R R L L U D L D D D in main menu 
U = Up
D = Down
L = Left
R = Right
It's the fist part (and the most important part) of the answer ... this tip is given at the end of the 'normal' game.
Now, the rest is very simple ....
Well, I don't know whether you need to do something special. Doing that key combination you enter in the test mode, where you can select easy or hard mode, and try the sound test.
Yes, I can view it as the complete answer.
By 4 steps, I meant :
1 - Press the arrow keys as you have mentioned
2 - Go to option 2 of the test mode and select the hard mode
3 - Go to option 3 to quit the test mode
4 - Play the game of course 
I've played the game with my cheat in both modes on MSX and SG-1000 (different arrow keys on SG-1000). The game is already hard in normal mode, it's crazy in hard mode and at the end of the hard mode you have another message, but there's no super-hard mode 
So, Guillian, it's your turn
Which game does use the WonderCard?
The WonderGame?
Wonder Boy ?
Doramus? :\
