How to change Dynamic CRM user interface from Classic to UCI mode

If you would like to switch back from OLD Classic UI to new Unified Client Interface (UCI), you can have two options

1) Adding an additional form parameter forceUCI=1 in URL to resume to UCI mode.

https://vjCityTest.crm4.dynamics.com/main.aspx?Origin=Portal&page=Settings&area=nav_administration&forceUCI=1

2) Change the System Setting Under Administration accordingly.