If you register an account and you make a deposit you will start staking automatically. There are no restrictions about when or how much to deposit/withdraw.

To participate in airdrops you need level 3 verification, and to get that you need a $5 worth deposit. It's like this just so that people don't create multiple accounts.

To participate in the lottery you need level 4 verification, but to get this you just need to get 10 stakes so you will get it automatically soon after depositing your coins.