Objective-c - Volume limitation and volume adjustment issues during iOS recording

Question

I am working on a recording-related function. Since this APP is for children, I hope to achieve this effect:

1. After clicking the button to start recording, if the user speaks at a very low volume, it will be regarded as invalid input, and the recording will not start until the volume reaches a certain value. (You can also use certain methods to cut off the silent parts before and after the recording is completed). After all, children's operations cannot be too accurate. They may press the button and not speak for a long time, or they may have finished speaking and still press the button and not let go.

2, I hope all recordings can be output at a uniform volume. Because children may not speak loudly, which can meet the recording requirements, but their voices are still relatively soft. So I hope to do a whole standardization.

I would like to ask, is there any relevant interface or code that can achieve the above two requirements? The second requirement seems difficult to implement because Apple does not allow adjusting the volume through code. I don’t know if that’s the case?

Could you please help me answer this question or provide some solution ideas?

Thank you very much! !