When in 1.3 mode, is his A600 then an A500? Same memory setup?
Basically...
As for memory, a plain A600 with 1.3 is like an A500 with 1M CHIP RAM.
There are some old games that don't like anything other than 512k CHIP.
If in Kick1.3, how does he activate his hard drive from Workbench (Compact Flash)
He doesn't. It's A500 compatible and the A500 didn't have IDE or Compact Flash.
Degrader is the best option to get as close as you can for compatibility.
And WHDLoad if he has enough RAM.
desiv
(Now, you could try to burn your own 1.3 ROM that has the IDE (scsi.library??) from 2.0. I think that might work?

(not sure).. If that library doesn't also want a bunch or other 2.0 libs in ROM to work. )