H-1B Visa

I am currently working on H1B visa, My current visa stamping is via my previous employer (Employer A) and valid till September 2017 and my I-797 is via my current employer (Employer B) ,its valid till August 2018.
I have few queries regarding my new H1B visa stamping and I-94. <br>
1. Can I get my visa stamped in CANADA or any other country nearby to USA without revisiting INDIA.<br>

2. Am I eligible for drop box option for my new stamping as my current stamping is via my previous employer.
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3. I can see also my I-94 expiring is September 2017. Do I need to reach out to USCIS to update it, in order to maintain my status.

I have a question on H1B stamping. I am currently working with employer A. I have visa stamping till Nov 2018 and it shows the name of my previous employer, employer B. I am planning to visit India in the coming month of November 2017. Should I go to visa stamping and get a new visa showing a new employer, employer A? In the past, I have encountered a similar situation and I came back successfully with out getting a new stamp. I am not aware of current immigration law. Have there been any changes in this aspect?

I have approved I-140 with company A and my wife has her I-140 approved or over 2 years. I'm planning to move to H4 EAD. Can I file for H4 and H4 EAD concurrently? What would happen to my earlier I-140 and also to the GC process if I am on H4?

My dependents visa stamp on passport expires on Sept 1st 2017 and have valid I-94 till Sept 1st 2017 and this was with the previous employer A I worked for. I moved to a different employer B a year back and haven't filed H4 for dependents with employer B as it was not necessary. Now if my dependents travel to India prior to Sept 1st 2017, do I still need to file for H4 extension or is it good if they attend the interview at consulate in India and get visa stamped on passport without H4 extension using my approved I-797 (till 2019) with employer B.

I have an approved I-797A with company B valid till 2018 May (attached i94 with same dates). My Visa with Company A valid till 23 Aug 2017 (old passport). I got a new passport in 2015 Dec, which I have applied after moved to company B. I traveled to India in June 2016 and comeback, CBP officer gave me I-94 till 23 Aug 2017 with new passport entry, because of new passport I-94 number changed. My question is I-94 (May 2018) is on my I-797 is still valid or it will valid only till 23 Aug 2017? If valid only till 23 Aug 2017, How to solve this issue with out going out of the country.