SharePoint 2016 - Copying content DB from Prod to Dev - sharepoint

Question

I tried to copy the content DB from Prod to Dev server for the first time in my SP 2016 environment. Both the environments build versions are same (16.0.4705.1000). However in the prod under "Manage Patch Status" I see one extra Feature Pack 2 patch (16.0.4588.1001).
https://support.microsoft.com/en-us/help/4011127/descriptionofthesecurityupdateforsharepointserver2016september12-2017
Now when I am doing Mount-SPContentDatabase, I get the following error.
Mount-SPContentDatabase : An extension defined in the database is not registered with the farm.
In the ULS I see the following information. It says the project server database extensions are missing.
Following are my questions,
Is this because I have installed Feature Pack 2(link above) in Prod which has security updates for Project server? We don't have project server enabled in either of the environments.
Can I install the Feature Pack 2 in Dev now even though it has higher security update already installed? Isn't the later patch includes everything that was released in the previous patches?
This is just for my understanding. In the manage patch status why does the Install Status for feature pack 2 shows as "Superseded" even though I have other later patches?
Tried Restore-SPsite as well but getting error "The extension set does not match."

Answer 1

Had the same problem during the migration from 2016 -> 2019.
My solution:
Register the missing extension https://techcommunity.microsoft.com/t5/sharepoint-support-blog/upgrading-a-content-db-from-sharepoint-2016-to-sharepoint-2019/ba-p/1374209 (look at the bottom of the post)
remount the contentDB
Required code to perform the registration in step 1:
Check extensions in old farm
$contentservice=[Microsoft.sharepoint.Administration.SPwebservice]::ContentService
$contentservice.RegisteredDatabaseExtensionTypes >> SP2016Farm_registered_Extn.txt
Check extensions in new farm
$contentservice=[Microsoft.sharepoint.Administration.SPwebservice]::ContentService
$contentservice.RegisteredDatabaseExtensionTypes >>SP2019Farm_registered_Extn.txt
Register missing extension in new farm
$svc = [Microsoft.SharePoint.Administration.SPWebService]::ContentService
[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.Office.Project.Server.Database.Extension") | FL
$svc.RegisteredDatabaseExtensionTypes.EnsureAdded([Microsoft.Office.Project.Server.Database.Extension.ProjectDatabaseExtension])
$svc.Update($true)
In my case i did the steps below before i have registered the missing extension, but i think/hope there is no need to do that.
Powershell: Enable-ProjectServerLicense (Trail License)
Check running Sharepoint CA > ProjectServer Service
Check/create Sharepoint CA > ProjectServer Application