Data Validation Unique Value

Hello,

I need help to fix the formula related to data validation.
I have a table, and i want create dropdown list ( data validation),

Current one ( with yellow highlight) is the dropdown with offset function to make it dynamic,
however, the data contain duplicate and not sort, try few formula to make it unique but not success yet.

Attach is example of the sheet.

Would be great if you guys can help me.

Thank you very much.