If you Have installed a Launcher e.g. Unity Launcher on Your Device, you can easily back to ubuntu classic Desktop instead of new launcher that previously installed. This is one of best answer i founded in askubuntu.com.
- Log in with the classic GNOME session by selecting your username and then selecting Ubuntu Classic Desktop: 
- Right click the - Main Menuapplet (that is the one you want to have replaced) and select- Remove From Panel. 
- Right click the - Indicator Applet Application Menuapplet and select- Lock To Panelto unlock it. 
- OPTIONAL: Remove it the same way you removed the - Main Menuapplet 
- Right click on the panel and select - Add to Panel... 
- Select the - Menu Barapplet and hit- Add 
- Right click it and move it to the left
- Right click it again and select Lock To Panel
- WIN
Note on point three. It is optional. If you don't remove it you'll still have the Indicator Applet Application Menu applet displaying all the menus.
- If you want to permanently revert all the menus to the classic style you can also remove the indicator-appmenupackage.
To permanently make the Classic Session be the default, run the Login Settings tool and select the classic desktop:



