During game play just pause the game and press the following codes:
Code -- Effect
ABACCACB -- Kill the enemy
AABACAAC -- Open doors
(They also have a third code but it's a password.)
I tried these, they work in the European (Mega Drive) version only.
I found some more here: http://www.sega-mag.com/astuces-Prince+ ... 1784-3.htm (French)
CACBBACC -- Get one more HP, like a small potion.
BAABCBBB -- Shake the level, like that special potion.
Plus the two codes from gamefaqs.
Another list: https://archive.org/stream/Game-Power-3 ... 1_djvu.txt (Italian)
This lists all four codes above.
Um... If I scroll down on the aforementioned gamefaqs page, there are more codes there:
BBAABCCB -- Adds a life bar
BAABCBBB -- Create earthquake
CBAACCBA -- Halts time
BACCACB -- Kill enemies
BACAAC -- Open doors
CBAACBAB -- Skip level
CABBBB -- Slow motion falling
This lists almost everything I found before, except the code for one more HP. Plus of course it has new codes.
They all work in the European version.
Note how many of these are potion effects, including those potion effects that are limited to the European version.
Interestingly, slow-fall seems to protect the prince from spikes.
Although this is also true for the slow-fall caused by potions.
Looks like the leading A's are not needed?
Let me guess: In the key-buffer, A is stored as zero, and the buffer is initialized to zeroes?
The leading A's are required, though, if I pressed B or C before entering the code.
Now, I wonder if there are more codes, or any codes for the USA version...