@freqmax
3.5 would be the same requirements as 3.9 I would've thought... The core files (i.e. kickstart) should be able to run on any CPU and chipset - KS 2 and 3 simply disable the options related to chipsets and screenmodes which aren't available. The other way around (KS 1.x in an A4000) should work too, though you'll probably have trouble with hardware not being supported as 1.3 doesn't support the newer AGA chipset or onboard storage interfaces, so no SCSI or IDE hard drives, no PCMCIA, and possibly no Zorro III (not sure about that?). Physitally you might also have trouble as AFAIK the 1.x kickstart chips were single chips accessed in 16-bit words, whereas the A1200 and A4000 both use a 32-bit configuration requiring two kickstart chips. It would be a simple matter to soft-kick an A4000 to 1.3 and see what happens
I think the only things requiring the 020 in 3.5/3.9 were the contributions, add-ons and the likes, so if you don't bother with these you're probably alright (if a little slow) on a 68000.
As for build and release numbers - Release numbers are generally only changed for major updates, and are a nice, overall reference for the whole release including all its files. Build numbers are usually more closely related to the internal development of the code, being incremented each time a new version of that particular file is written. Which is why there are a few different versions of the 3.1 kickstart - they're all 3.1, but each is customised for a different machine, and so is a different build number. In Amiga land the build revision numbers of the files consist of 2 numbers, the first relates to the release and the second is the build/revision. So, 1.3 files are all 34.x, 3.0 files are all 39.x, 3.1 files are all 40.x, and so on...
