in the case of such big wins do users have to provide any complementary informations, and how the wins are paid ??
Looking at the first few pages of the thread, OP said that they do not require KYC when someone won a lottery.
In basic terms, we pay the insurance company a significant premium and send them the ticket numbers. If the winning ticket comes up, they send us the money to pay out to the winner. This is why is takes a little more time to get a jackpot out to a player than a standard withdrawal. We don't provide any personal data to the insurer, and so we can pay it out to an anonymous player.
Also, if you look at the first few pages of the thread, there are other bitcointalk members who have won the lottery and get paid
[1]. But, the thing is, their promotion here in bitcointalk as well as from their social media account seems to be inactive. It would be better to proceed with caution.
[1]
https://bitcointalk.org/index.php?topic=5235985.msg54764304#msg54764304