If you use the same enumeration in different attributes of your entity the selections will not be linked. So create 6 attributes of type enum and connect them to the same enum and add the 6 dropdowns on your form.
I don't think you can. You could replace the enumeration with an entity. In the after startup you create the different values. Then create 6 associations between this new entity and the entity the enumeration was on for every dropdown. Then use a microflow to limit the entities a user can choose from based on the other associations.