When we set different fields as required for free vs. paid events, the same required fields show up for both. For example, for a free event, we set the address field as required. For a paid event, we didn't. But the free events show on the front end with the address field optional.
I will assume that you do not have the latest build of DT Register. If that is the case, please upgrade. If you DO have the latest build, then please submit a support ticket. Thanks.