i am working on project which allow users to send Some BTC to "xyz" address and allow each users to send etc to separate receiving address.

question 1: can bitcoind generate multiple receiving address with just one private key?
question 2: will all Btc End-ups in same wallet (Parent address/Parent private key/can use all transaction as single accumulated received Btc)
question 3: will i be able to send/spent all gathered etc from just single Private key?