Is it required to have an electrum account for electrum api usage? Is it necessary to have an account on electrum in order to build a custom BTC wallet interface using electrum-apis where user can create multiple wallets, address, send/receive transactions?

Or, there is no login credentials required for me to integrate all the features of Electrum into my application?
It is an open-source software. There's no need for credentials or accounts. 

There's multiple public electrum servers you can connect to through your electrum wallet. You could build an interface on top of the electrum wallet that connects to any of these servers.