Could we for instance just slightly bow our head instead of doing what we would normally do when we enter and leave the prayer hall, or must we bow completely, or should we only do the action with our hand as opposed to slightly bowing, or can we just say "hayzinda" and not do any action (but I think I heard in a hadith that we should bow when we enter the place of prayer - is that correct?), and if we say "hayzinda" under our breath - or not very loudly is it "worse" than if we said it at an average volume or is it better to say it very loudly - what about 'saying' it in our head? And what about the other times, why is it necessary that we do these actions?
Just one more thing - why do we do sujood after and before "dua niyat khair" - is it sujood or is it not supposed to be that at all but we should bow down anyway - maybe only halfway - or we only do the hand action - or maybe we are really supposed to just keep our hands raised and not change them from the "dua niyat khair" position while not bowing down at all, or do we only do the hand movement and nothing else (have I covered all the combinations

I am most anxious to hear your answers - thanks and Ya Ali Madad!
-Shariati Shafiq