Hi - to use a data validation list on a different worksheet, you need to use a named range. So instead of putting your offset formula into the data validation box, create a named range and put the offset formula in for the named range reference, then your data validation formula is =named_range

I don't believe it is possible to remove duplicates from a data validation drop down directly, so you would need to create another table to give you a list of the unique entries and reference your data validation list to that table.