Say if someone owns 10 Bitcoins which is not declared and government doesn't know about it (earned/mined etc but did not buy) and now that someone want to avoid paying tax on cashing it out. Can he simply move to countries where there is 0 tax like (UAE) specifically dubai and setup a company there and cash out crypto over years in dubai bank account and later decide to move to his home country with all that money. Since dubai has 0 personal tax and his home country can't charge tax on it because of non-resident of home country. Is this possible?
From what I've heard anecdotally, if you are or ever have been a US tax payer, the IRS will continue to hound you for a looong time, even if you change residence and become tax liable in another country.
That being said, if you're serious about tax optimization I'd recommend getting in touch with a professional tax advisor. As pointed out by FatFork, taxes, especially international taxes, can be very complicated, will vary from case by case and can come with a bunch of pitfalls that you don't want to fall into.
I think this sums it up, correctly. Since I became interested in the subject I see that there are several forms of tax avoidance, legal as you rightly point out. One of the ones I have seen most mentioned is the creation and sale of NFTs. It seems that cryptocurrencies open a whole new world for tax avoidance, and I am surprised that it has not been discussed more in the forum.
I'm pretty sure that the tax games and money laundering (the real kind, not the kind of "money laundering" that Bitcoin has been accused of in the early days) that NFTs enable are an open secret at this point; with people just keeping their mouth shut about it for fear of normies and governments catching wind of the effectiveness and trying to combat it.