Hi Biren! It may be best to align that picklist with SFDC's values to ensure proper data sync OR to align the SFDC field type to what users are seeing on the form (the multi-select...
Have you looked into visibility rules? These may be able to do what you're describing without custom coding:Dynamically Toggle Visibility of a Form Field - Marketo Docs - Product D...
Hi James - you could add these records to a static list, based upon the random sample. Then base the remove from flow step upon the static list membership.