Yes, only SNES version works as it should, Swimmer Mango Booter just start to swim in the water and after he came out of the water is just walker (and Swimmer as it is permanent skill) again.
On the practice skill selection screen you can't select 20 of them. It's only possible to select each skill just once. But when the practice level starts there are 20 (or 99, depending of the version) of each selected skill to use.
There is a problem with selecting skills for practice on the PC (and just on the PC) "Insufficient Memory" message can occur on some skills depending on which skills are already selected. Like, some skills require more memory then others. But, the PC version is the only one where it's not necessary to select all 8 skills for the practice.
Time given for the practice levels is also not the same in all versions.
PC and FM Towns 9:00 (except Egypt 9:01, strange isn't it?)
Amiga, Atari, Archimedes 9:00 (except Egypt 9:01) but timer doesn't counting, so it's actually endless.
SNES 5:00
Mega Drive 3:00
And some more interesting facts:
SNES, Mega Drive, GB, GG and SMS do not have color inversion for the permanent skills.
Atari ST is only version without Intro animation and End animation.
SNES is only version with the background graphics on the levels (except for the Classic tribe) and only one with snowfall on the Polar tribe (simple but nice effect).
FM Towns is only one with a 'real' flame on the Jet Pack skill. Just dots on the other versions or even nothing on SNES, GB, GG and SMS.
I have already mention left and right Twisters on the Mega Drive.
And certainly plenty more details, I don't want to bother everybody with that things any more.