Thank you. And If I want only 3 day access, do I need to activate it at the beginning of 3-day period or is it possible to activate now and to be valid from December 25th (1st day of champs)?Ah, you misunderstood the info about the channel numbers (or I probably didn't express this clearly enough)!
On iSakura Pro Plus you have to switch between channel 66 and 5.
If you choose to watch via Japan TV Standard (the picture you posted in post #62) it's channel 62 and 7.
You only ever need two channels – Fuji TV One and Fuji TV (see picture with the caption "2020 Japan National Figure Skating Championships Broadcast Schedule". The two services (iSakura and Japan TV) are pretty similar and both have a replay option ("on demand" so to speak). Because the Japan TV stream just never runs stable for me, I recommended iSakura instead, which in my personal experience has always been reliable.
You don't need a VPN for either iSakura or Japan TV.