Can we get any default address before running getnewaddress? I am trying to develop some application using bitcoin (currently only in the regtest mode). 
I am aware that one can create a new address using 

bitcoin-cli -regtest getnewaddress

RPC call, but I want to know whether bitcoind pre-generates a bitcoin wallet address when we install and run 

bitcoind -regtest -daemon

fresh. If yes, how can I know this address?
No.

The wallet actually always pregenerates keys (not addresses) and puts them in the keypool. A keys is fetched from the keypool and converted to an address only when an address is explicitly requested (via getnewaddress or from the GUI). An address is not pre-fetched by default.