MCT8316AEVM: How is accuracy of the internal oscillator?

Hi Team

How is accuracy of the internal oscillator?
How is the temperature characteristic?

Also, I have some questions about, "External Crystal Oscillator mode" and "External Clock Source".

External Crystal Oscillator mode:
Only use two seconds for calibration after booting the device?
Not use after calibrated?

External Clock Source:
Only use two seconds for calibration after booting, like external crystal .
Is my understanding correct?

Also, the external clock source can be the PWM output from the MCU？
Is there any problem or conditions？