The ST version was done with STAC, whereas the rest were coded in GAC. The C64 version was ported by Mandy Rodrigues.
The graphics for the ST version were produced by Dicon Peeke.
Steve Clay referenced an Amiga version of Shymer in his Amiga column Adventure Probe a couple of times. This seems to have been released by the Central Licenceware Register (CLR) through PD libraries. It's described as a graphical adventure but no authoring system is listed. Advertising states the game was on CLG 27 and LPD30.
[+] Users currently playing this game
Based on nursery rhymes, some fairly obscure. Googling them was not always helpful. Luckily the game is fairly linear, ie get required object for character, they will then give you an object for the next character