Slow process of diagnosing this: information here is a summary of my treatment and helped by top neurosurgeons, physiotherapists, couches and other professionals. You can read my diary below. We are trying to get me back to games fast.
[24th June] general doctor order me 2 weeks of rest with anti-inflamatory painkillers
I am doubtful about this because I cannot see inflammation. I try it and fingers developing some pain after being in the mold 1-2 days.
[26th June] no inflamation whatsoever so my couch instructs me to prepare me to use the hand normally
Stiffness in the little finger and ringer finger and pain in the little finger when trying to put into fist after being a long time in alu mold. Too stiff shoulders: cold in shoulders relaxes the ring finger. Hot in hand relaxes the stiffness in little finger and ring finger.
I am feeling totally normal again and sleeping with alumium fold again so the fingers get oxygen during sleeping. Goal is to get better in one week like pros.
Misc information
Different Stretching Methods
1st method
Push-ups with fingers feel very very good to the fingers, this is because deadlifts with about 90kg require a proper warmup.
2rd method
Rise-bowl-scrutching-method suggested here warms up the whole hand and actually simulates the handles of different sized rackets -- unfortunately the shape of crutching rice and crutching handles of rackets are not the same so not specific to the ring-finger-little-finger-area.
3th method: Static stretching
Stretching like here but at least 30 seconds' interval so it takes at least 20 minutes to stretch just one hand. Excellent stretching also here by a rock climber, it feels excellent!
Different relaxation methods
I. method: resting during rock climbing
A rock climber shows here advanced resting techniques for hands. It may be possible to adjust to other sports: hands slowly down and then hand up here crutching hand push the fresh blood back to the hand.
Different coordination methods
A. method
Powerball is not sufficiently powerful/large to train my fingers on my serving hand. It certainly makes fingers a bit more flexible in the left but I think the main thing it helps with is coordination, it actives areas of hands which may not be under normal usage during day and sporadic spinning requires proper coordination or bad sounding noise generated.
Related Threads and material
Rehabilitation for Ulnar nerve, awesome stretching movements in the video "Ulnar Nerve Flossing Exercise - Amazing Results - Kinetic Health" here.