Need Advice: 3 GBPs, Changing Names, Three Different Businesses | Merging Businesses

[Syed Amir]

There are three different businesses, with different names, different GBPs in different cities. Now these three businesses are merging.
So we need to rename A and B to C’s name in GBPs.
Questions:

1. Prerequisites: What steps prevent GBP suspensions/reverification?
2. Documents: What’s needed for name changes/reverification (e.g., licenses)?
3. Citations: We’ve updated most citations. What else ensures consistency?

Please share insights & experiences. Thanks..!