Hi @Silvia80
Your test is interesting, but we need somewhat different movements for playing. The major movements are on the two larger knuckles, and then we want good flexibility to be able to bend the smallest joint at the finger tip so we hit just one string. What you appear to need is to get better control over independent motion.
We don’t really need our fingers to straighten. In that respect, your flexibility is better than mine. I have trouble with triads (if you are that far into the lessons) where I need to flatten the tip of finger 1 against strings 1,2 and then cleanly fret string 3 with finger 2. This is the stretch I think is important - but maybe it is just my hand and not yours.
You mention doing the finger gym. Those are really good. I also have another exercise that is similar I outlined in item #3 here: Older Beginner Fret Board Issues - I can't land my fingers on a chord at the same time - #15 by sequences.
It helped me get better control over my fingers. I still have plenty to work on when swapping fingers 3 and 4, but at least I can do it now, even if I need to concentrate on it. I don’t do this very often now. I seem to be doing ok with what independence I now have, but will go back to this daily if I find something I need to work on.