Are you saying that before trying to set focus at infinity in CHDK I should set AFL (to infinity? or just set AFL, regardless what the focal point is?), only then CHDK infinity setting will work correctly?
AFL does not set the focus to anything specific. It just tells the Canon firmware to lock the focus at whatever it is currently pointed at and not make any more focus adjustments. This function is available in pretty much every Canon P&S camera and is not something CHDK provides.
Or that Canon AFL is to be used whenever CHDK infinity focus doesn't work?
The reason I suggested using it is that once the Canon firmware stops adjusting the focus, then CHDK can do so (via scripts or menu settings) without the Canon firmware either ignoring the CHDK setting or changing it after CHDK has tried to set it. This does not always work in every cameras and on many cameras is not necessary. So you need to experiment a bit to figure out what works for you. We are trying to change that but progress has been slow lately - I'll see what I can do about that.
As for v1.3, I'm a little bit concerned in using it, since I understand that it is an unstable version. Do you think I should try it? Does it increase the risk of bricking the camera, or it means only more potential bugs?
Today, v1.3 is where we put the shinny new stuff. However, the new stuff tends to be carefully vetted by the various developers and is usually fairly low risk by the time it gets into the autobuild version. And we are almost ready to make v1.2 obsolete by declaring v1.3 to be the new stable version.
FWIW, I only use v1.3 on my five or six cameras. And doing CHDK development over the last five years or so, I've crashed my cameras more times testing new code than I can count. If there is something bad CHDK can do to a camera then I've probably done it. A few times. But so far, no bricked cameras, although by tomorrow that could all change. It just does not seem likely.
So yes, by all means use 1.3 - especially if you want to experiment with focus settings.