To send ether to a contract without a function call:
A.
a fallback function must be declared and it must be made payable. If there is no fallback function or the fallback function is not payable it will throw an exception.
B.
either a fallback function which is payable exists, or no fallback function at all exists.
C.
you cannot send ether to a contract without explicitly calling a function. The fallback function can never receive ether.
great, because they cut the middle man, run on a trusted platform, apply logic to the blockchain where already economic assets are running and thus allow peer to peer trade.
B.
an amazing way to create new applications. Those applications run entirely separated from other applications on the platform and allow for logical interactions. They can't access any funds to add an additional layer of trust.
C.
a new way of applying logical operations for banks and big financial institutions. This way they can reduce the staff while operating at increased security.
Keccack256 while internally to hash values it's easy to use the Dagger-Hashimoto to create a meaningful hash.
B.
the Dagger-Hashimoto hashing while internally the EVM uses SHA256 which is an alias for Keccack256.
C.
the Dagger-Hashimoto hashing while internally the EVM uses Keccack256 which is almost similar to SHA256, but has a different padding so produces different hashes.