Amiga 600 with kick 1.3, is it 100% Amiga 500 compatible?

[Jope]

I believe someone did get it working in 1.3
 
However an a600 with 1.3 isn't going to be amazingly compatible. The lack of c00000 memory for a start (you may be able to hack the motherboard to get that working though).

The way to get c00000 memory is to install a RAM board on top of the CPU which provides this.

Basically that is the biggest compatibility improvement you can make.

[psxphill]

I think ultimately your best solution if you want 100% A500 compatibility is to just pick up a cheap A500 off ebay, and give your A600 to me.

Getting an a500 is probably the best way, but even then you have to make the choice of kickstart 1.2 or 1.3 (or fit both)
 
An A600 isn't particularly useful either for a500 floppy game compatibility or using WHDLOAD. I've always wanted one because they look cute, but I can't imagine I'd ever use it.