Learn English – Which is correct ‘once you have given to me’ or ‘once you give me’

Among the three samples you have provided, the middle one is correct:

I will update you once I reach my home.

The first one is wrong because you are mentioning there that you'll do something in the future after you do something in past(which of course doesn't make sense).

Same situation arises in the third one.

Again, as @StoneyB mentions:

get is a much better choice here.

Because How to you do? is all but dead. But when it is/was used, you only use it for someone you have never met before. And thirdly the proper response to How do you do? is How do you do?

After the greeting Hi, the question How have you been? is natural and actually used.