1/ The ADuC814 ADC example code uses an interrupt to detect the A/D end of conversion. What bit should I read to detect the end of conversion without interrupt (ie just a loop reading this bit until completion of the conversion) ?

Bon jour Jean-Michel,

I'm not familiar with ADuC814, but have running a loop to detect completion of conversion is probably no good idea, because mcu should completely 'rest in peace', as long as internal ADC is working. So, interrupt controlling is highly recommended.
If MCU performs your loop while ADC is working, a heavy loss of accuracy is to be expected. This is valid for most of all microcontrollers having an internal ADC. Very probably also for your ADuC814.

Bye,
Kai