Why wasn't there any oxygen in the beginning of the Earth? In the total beginning of the Earth there was CO2, N2 and H2O. So there was O2 but always in bond with Carbon and hydrogen, but what is the reason for that? Is O2 always reacting with free carbon atoms?
The temperature of the Earth was is those beginning days around 1200degree Celsius. Is that also a factor of those bindings?
The 1200 C temperature is a big clue, given the auto-ignition temperatures of most "stuff". https://en.wikipedia.org/wiki/Autoignition_temperature

Any "free" oxygen would immediately "burn" with carbon and just about anything else, yes.