How to reinstate the GD&T if no CAD model command in Qualify 2012?

You can add this function back to the User Interface.

1) Go to Application (Swirl Icon) > Customize.

2) Drop down the menu and select Tools

3) At the bottom you will see the GD&T button.

4) You can place this function anywhere in the UI.

After a restart you will see the command and can use it like before in v12.