Testing in odoo v12.

For example: 
A is Fresh Database, soon to be production
B is a duplicated database from A for testing purposes
C is My Friend database who did initial studio modification

In this case, my friend creating a studio modification in C database > export > give it to me.

I put it in database B to test, it works great and I do the small adjustment with studio too here in database B. After, I do export and ready to put it to database A because I think it will works.

But it cannot work like this, database A can see all database B modification but cannot see all modification comes from database C as a studio data.

The error on database A will be like "Missing field x_studio_xxx/" which originally made in database C.
Why ??

If it should be a 1-way import-export feature for studio modification, how do we work as a collaboration with odoo studio as we need a lot of test databases? Any solution ??