Welcome to Amiga.org. Yes, you can have AmigaOS 3.9 on your A1200, but you do need to buy additional hardware to allow the use of a CD drive, or connect to another computer that has a CD drive to install the files. A stock A1200 has a 68020 CPU installed but there are accelerators available (used mostly) that use 68030, 68040, 68060 and even a combination of 68040 or 68060 and a PPC 603e CPU's that you can install to speed things up and allow use of some newer software. Most software available will run on the 68020, but some need faster CPU's and more importantly, more RAM than the stock 2mb of Chip RAM. There are PCMIA network cards that will allow ethernet connection to another computer or you can use Null modem cable too for transfering files. Good luck.