After the TT Core SDK initialization begins, it downloads:
TT Core SDK synchronizes the Order Book and positions by account. As such, any given account can be used to trade without needing to wait for all accounts to be ready.
If you want to receive order / fill events for all solicited and unsolicited orders, you need to use the ttsdk::IOrderBookEventHandler interface.
If you want to receive order/fill events for only those orders that you choose, you need to use the ttsdk::IOrderEventHandler interface.