- Write it with an .ISO image;
Correct
- Don't use CD-RW (rewritable);
Correct again. :-D
Back in 1993 I don't think that CD-RWs do exist, so CD32 can't read them.
- Use the lowest speed to burn it. If your burner program accept 2x, use it!
As I said, I burned around 30 ISO games from BTTR site in 8x speed and they worked fine at all. :-o
- Avoid those very cheap, brand-less CDs made in Taiwan, China or related ("industrial media").
This is the FIRST rule. Never use no-name media. These days even brand media (TDK, Verbatim) are very cheap, so why to risk it?