Can everyone join the sale,or there are some restrictions?
Standard restrictions for US and China as always, time will come when that will change again.
But this will not happen soon. Many countries continue to be wary of cryptocurrencies. They need full control over the turnover of the cryptocurrencies so that they can impose taxes on them. And it is very difficult to realize in real life.
Of course, this will not happen any tome soon, and some countries will remain forever out of this market...