Do I have to power-on reset CMOS counters?
You have to assume that if the datasheet doesn't specifically mention a power-on state, that the state of any digital logic is undefined at power-on, and you need to provide a reset pulse to get it to a known initial state.

Generally speaking, only single-chip microcontrollers implicitly handle power-up initialization. However, you can purchase tiny power-up/reset controller chips that will add that feature to any circuit.