Ethereum does not have a concept of UTXOs - there are only balances. So once an address receives Ethers it is added to its balance and any amount can be sent out (which is smaller or equal to the current balance). So you can use one transaction to send any amount of Ether out of an account.
No, they use a different algorithms to generate addresses.
No, you cannot use a bitcoin address to receive ethers, or any other cryptocurrency.
Yes, there are "Hierarchical Deterministic Wallets".
For Ethereum see this: How are ethereum addresses generated?