Hi, Do you have to add liquor to the ice cream recipe or can the sugar from the condensed milk keep it from icing alone?

Sounds like you are making a no-churn ice cream with sweetened condensed milk. In that case, the liquor is there for flavoring. There usually isn't enough of it (couple of tablespoons, maybe?) to affect the freezing point of the ice cream. So you can probably leave it out. The reason the no-churn ice cream stays soft is because the water content is on the low side. You've got heavy cream and condensed milk, plus the sugar in the condensed milk (and there's a lot of it) will help control the size of the ice crystals, keeping them smaller, which will give you a softer consistency.