You have to use the 3rd party tools to migrate / move content between the SharePoint tenants. Their is no OOTB way, you can try different tools as they offer free trail
Another way is using the Save as template method.
Save the source site as a template
Then attach the saved template to the destination site in SharePoint
Copy the content ...
There is a chance that the list itself is broken as well.
If it is the default list web part, delete it from the Web Part Page Maintenance page and then try opening the list again.
See a similar post here:
How to fix error “The page you selected contains a list that does not exist.”
To move the lists and libraries between environment, I would suggest you use the mover tool. Please read this article for more:
For SPFX solutions, you could download them from the test environment. Then deploy them on your product environemnt.
SharePoint Migration Tool << Be careful with this, its just as slow as the other methods, but when it finished successfully, your files are nowhere. Seen this happen in 3 different companies all were transferring 100GB+
In my opinion, sending a drive to M$ with the data on and asking them to do it is the FASTEST way. Drag and drop via sharepoint is ...
You can use Move-SPUser or stsadm -o migrateuser to migrate from one account to another (if using Windows claims, make sure you pass the -IgnoreSID switch for Move-SPUser).
There are other tools, such as Sharegate, which allow you to remap user accounts from one object to another.