Do you have any restrictions on age for participation?
Yes. There are two restrictions. It is not allowed for citizens of the US and Canada and for underage persons.
no restrictions for korean citizens as I understand?
Yes, there are no restrictions for korean citizens.
What level of KYC will be required? what documents are needed?
Full KYC willl be required. You will have to provide your personal documents ( passport, driver license or ID-card of your state and documents, proving registration on a residence).