None: there are strictly no setup fees and crypto-currency deposits are free of charge.
To answer your question, Bitcoin is only the "deposit method" when making a deposit.
Be very careful with overly attractive returns.
To be credited, your bitcoin transaction must be first confirmed by the network. This process, which does not depend on us, can take from a few minutes to a few hours (sometimes even more, depending on network congestion and transaction fee you have entered).
Upon receipt your funds are automatically invested (placed in a pool, usually within a few hours).
I read here that "The interests for the current month (Direct Interests = on your balance + Referral Interests = on godchildren) are calculated on the last day of the month at midnight (and not on the run of the river) and are then added to your current balance."
Only one withdrawal per month is possible, debited from your account and sent on the last day of the month. This is because your funds are automatically placed in arbitrage pools from the first to the last day of the month, and it is too complicated, from an operational point of view, to make withdrawals during the month.
Yes, there are no restrictions.
The link is valid as long as the referrer's account remains open.