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?
Yes it's possible and completely legal but go through the laws of your own country to return money from zero tax country to your own cause some countries charges taxes or allows only certain percentage without fees. Well you can do that without moving to any country as well by using decentralised P2P platforms or finding someone who is trusted and can be traded in person in your country itself but I am not encouraging anything illegal or evading taxes.