No idea why it doesn't boot on an A1200 unless the floppy isn't hooked up properly tho.
in A1200 it does not boot because A1200 emulation is heavily incomplete, iirc.
should it boot on the A1000 or is the A1000 closer to the A500?
A1000 is the oldest one, you need a kickstart disk before the workbench disc (unless like Anna you have one which is compressed all in one)
A500 was the first real mainstream home system, which boots WB1.3
A500+ was WB2
A600 was similar to the 500+ but without the numeric keypad.
A1200 was the 68020 / 2MB Ram / AGA / WB3.1 model
CD32 was the CD equivalent of the A1200 (you could even get a keyboard etc. for it) and had MPEG decoding for some video based games.
A2000/3000/4000 weren't really home models and fit somewhere between.
For basic gaming your common setups are
plain A500 with 512kb memory expansion
A500+ with memory expansion
A1200 with various CPU / memory expansions / HDD (for the later games some of which really needed crazy CPU power compared to the stock model, afaik you could go up to 68060 during the regular life of the system)
CDTV (A500 level tech standalone)
CD32 (A1200 level tech standalone)
Additional floppy drives were also common, although not all games could make use of them (due to copy protections or bad programming) also the additional floppy could cause some incompatibilities due to extra memory use / bad programming so they usually had an off switch ;-)
All the fancy extra graphic adapters again are mostly for business use / graphic application / after market stuff, not games and usually cause massive incompatibilities.
A1200 wasn't compatible with a lot of early A500 software, again due to copy protections / assumptions that kind of thing. There were various kickstart emulators which would boost compatibility although anything relying on CPU speed would often run too fast. There were even A500+ compatibility issues with some, but that's less common. A600 isn't really recommended due to the lack of the keypad which renders a lot of software unusable.
That's why once MESS starts having software lists for these platforms (which will be huge and scary..) there needs to be some indication of basic compatibility, because it could be annoying even on the original systems. Even with an A1200 HDD system even many HDD installable games had issues if your desktop was set to anything but the most basic lowest resolution / colour settings due to memory requirements, or because they didn't change screen mode correctly / couldn't close workbench to free memory due to some program you were running... People talk about boot disks for MSDOS based games, but I had a collection of them on my Amiga too. Not always the easiest systems to work with, especially later on in life ;-)