I found that my ST .75, with standard head, would run quite satisfactorily on diesel fuel. It did need the plug to be energised for starting, though. Once running, its performance was quite acceptable.

CR on a two-stroke is tricky. The charge is compressed before it enters the cylinder... I don't know by how much, though.

By measurement, my ST .75 has a CR of roughly 9:1.

Haven't tried the Gadjet. On the face of it, I can't see what benefits it offers; but I haven't done any real research into the developer's claims.