We all know, there are 2 types of cryptocurrency
1st: centralized
2nd: decentralized
The difference between them, centralized cryptocurrency is controlled by a government or a company. It has value only in the specific area under company or government boundaries.
Decentralized cryptocurrency has no connection with any state, government
But, the government of some countries are against Bitcoin and some are ready to adopt Bitcoin. So what would effect on Bitcoin if any government approved Bitcoin as a legal tender?
There is virtually no point in adopting centralized cryptocurrencies at least in my opinion, simply because of the fact that it's essentially the same as fiat currency - it's not backed by anything, its supply can be debased, and it's just totally controlled by a single entity.
Decentralized cryptos like bitcoin are going to be the trend in the future. These are the real store of values when it comes to an economic crisis because of the fact that they are not controlled by anyone and can't be abused.
Your last question didn't make much sense. I'll still try answering it, though. There is going to be no effect on bitcoin itself if it ever becomes legal tender in a particular country, but it will have an effect on those who live in that particular jurisdiction, as the legal definitions of bitcoin may change.