I've tried to calculate each of the desired values here in this example workbook. The values and your images (and dates) do not match so I can not align with the examples supplied in Excel but these calculations will hopefully get you going.
Two calculations of interest
Window_sum(countd(member_id]),-11,0) - this will provide the sum of the distinct count of member id's for the last 11 months and then the current month. Just change member id to Order Id for the other measure.
To compare the value calculated in this calculation to one from 12 months ago utilize the lookup() command to find the value from 12 months back. Lookup([measure],-12) and if that calculation already has the sum of the previous 12 months then you can just work with it. I hope the examples supplied are enough to get you going.
Note this workbook is in Tableau 9.3 - available for download here: - Alternate Downloads Site | Tableau Software
member_dummy_pv.twbx 33.8 KB