Hello RezaMalek, It is not possible to downgrade to a previous version of OE without contacting support.  To downgrade is a destructive process and can only be done via a support technician.
Hi guysI have a question about downgrade Unity 480 . Can I downgrade my Unity 480 from version 5.2.2.0.5.004 to the previous versions? if I can, how? Thank you, guys,  
Downgrade Unity 480-XT