H4 to H4 transfer

[tia.init]

Hi,

I have H1 visa and thinking to go for COS to H4 for number of reasons.

I have a dependent son who has H4 based on my H1 visa.

My questions are;

1. If I am in USA and go for COS from H1 to H4 visa, what is the process i should be following?
2. If I am in India and go for COS from H1 to H4 visa, what is the process i should be following?
3. Same for my son, if he is in India( currently, he is in India, visiting grand parents) and goes for H4( based on my H1) to H4( based on my husband's H1), what is the process he should be following?

Thanking in anticipation!
Tia