H1B amendment and extension approved without I-94

[Ram-H1B]

I am working in USA and holding H1B Visa. My employer submitted H1B amendment and extension on last year. It was approved without I-94 and it's valid from Feb 13, 2019 to Apr 30, 2021. My current visa and I-94 are valid till Sep-2019. I would like to know the followings,

1. When do I need to leave from US and re-enter to get new I-94? is there any grace period?

2. Do I need to go back to home country (India) to get stamping or I can cross border from Canada/mexico to get new I-94.

Please assist on this.

Edited March 28, 2019 by Ram-H1B

[adshah84]

If you have Valid visa you can go to Canada/Mexico and re-enter with new I94. 

[Yespi]

My situation is similar - amendment/extension received H1 without i94. But I have old one for a different state valid thru 2020. My employer fired me and now a new h1 is being filed with a new employer. Am I still legal to stay in the country while my new h1 is in progress?

Edited May 22, 2019 by Yespi

[Ram-H1B]

I just got canada visa. Can I cross border via air to extend my i-94?