This content database has a schema version which is not supported in this farm.

Error:
This content database has a schema version which is not supported in this farm.

Reason:
Once you have taken the backup from SharePoint 2010 content database, usually you will restore the database in the target SQL server.

After restoring the database, you will try to create new "Web Application" using the restored content database. In this stage, you will get the above error message.

Solution:
Your source SQL server schema and the destination SQL server schema might not be matched. So you need to update the "Versions" table values in the "Restored Database".

1. Open "Versions" table from any of the existing "Content database"  from the Target SQL Server machine in "Select" mode.












2. Now open the "Versions" table values of "Restored Content Database" in "Edit" mode  as mentioned below.

3. Replace the "Version" field value in "Restored Content Database" by "Existing Content Database" values from "Target SQL Server" machine.

4. Now you will be able to create new "Web Application".

Thats it...

Update (14-October-2013)
The actual reason for the above issue is the "Version Mismatch" of the SharePoint server. You need to apply the latest cumulative update (CU) of the SharePoint server in the destination SharePoint server.

In my case, I have updated the "SharePoint 2010 Oct 2011 CU" and then Restarted the Server twice. The application is started to work without any issue.

Unable to connect to the Synchronization Service.

Error:

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Synchronization Service Manager
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Unable to connect to the Synchronization Service.

Some possible reasons are:
1) The service is not started.
2) Your account is not a member of a required security group.

See the Synchronization Service documentation for details.

Reason:
The Forefront synchronization service user does not have access rights in the required permission groups.

Solution:
1. Open the "Server Manager"
2. Go to the Groups Folder
3. Select the "FIMSyncBrowse" group  and double click on it.
4. Add the respective user and Click "OK" button.
5. Do the same steps to add the same user for "FIMSyncJoiners", "FIMSyncOperators", "FIMSyncPasswordSet" groups.
6. Logoff your server and Login again.
7. Now you can see that if you click on miiclient.exe file, it will be displayed without showing error.

For More information, see the below screenshot:

That's it...