It cannot be used to date volcanic rocks, for example.
The rate of decay of N in 5,730 years (plus or minus 40 years).
It does not give dates of millions of years and when corrected properly fits well with the biblical flood.
There are various other radiometric dating methods used today to give ages of millions or billions of years for rocks.
In summary, the carbon-14 method, when corrected for the effects of the flood, can give useful results, but needs to be applied carefully.The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.