No, your crypto return address cannot point to an online exchange. Your crypto return address must be tied to a wallet for which you hold the private keys.
Note that you can, however, fund an investment using your online exchange wallet.
Bitcoin transfers do not happen on a binary basis like sending a wire. These crypto transactions have hundreds to thousands of confirmations from their networks to confirm that they are real transactions. CoinList waits for 6 confirmations to consider the transaction. For bitcoin, the network can be pretty slow so it can take anywhere from thirty minutes to twelve hours.
Ether transfers do not happen on a binary basis like sending a wire. These crypto transactions have hundreds to thousands of confirmations from their network to confirm that they are real transactions. CoinList waits for 60 confirmations to consider the transaction and this can take anywhere from 5 minutes to a few hours.