Do I need H1B amendment if I change team and move from one office to another located in same city but with different zip code?
Yes
yes
No if legal entity is the same, job role is in same family with at least 50% job duties overlap, location is in same area. Yes if either of those two change.
In case amendment is required, How to verify that a company has filed it?
Is premium for amendments suspended?
You need to file the amendment only if you'll be moving outside your metropolitan statistical area. So, i.e: Seattle, Bellevue, Redmond, etc is all fine. https://www.uscis.gov/archive/uscis-draft-guidance-when-file-amended-h-1b-petition-after-simeio-solutions-decision
No