Is it necessary for a university to be registered from a government to issue a degree/diploma certificate? Or are there any governments who offer free registration of universities online?
I want to open a blockchain university which may offer master and graduation level courses for free
You can actually open that right now since it is a Blockchain program, but except you register it as a decentralized system before you will have the freedom and not have any issue that much with the government, but if it is coming in form of centralization, I think that the time will come when government will be fully into this system and they would want to regulate all the things that has to do with Blockchain and by then, some of the degrees you have issue may be declared illegal.
It is better that you make registration for it and explain your concept to whoever is in charge of the registration, maybe they will hear you out and then approve your university. It is a great idea and I really wish you all the lucks you will have on this project, because we need projects like this.