Is it possible to transfer ETH(not erc20) by approve+transferfrom?
Im so confused about it. Does ETH support itself all erc20 standard functions?
Ether existed long before ERC20 standard was introduced, and Ether is not backed by any smart contract that could in theory implement ERC20 interface. Though, there are ERC20 tokens backed by Ether called WETH.
No, ETH itself is not ERC-20 compliant (it's the native currency, not an ERC-20 token).
One option would be to use something like wrapped ETH (wETH), which is an ERC-20 wrapper that allows ETH to behave as an ERC-20 token.
Yes.
Is it exactly like approve
-> transferFrom
? No.
You can sign a raw transaction with your private key in which you, as usual, precise how much ETH you want to send, to whom, how much gas, what data and so on. Once it's done, you can share this signed transaction to anyone you want and this person will you be able to broadcast it, and it will just like you made the transaction yourself.