Can I use alpine bindings in the park occasionally?

You can, but you won't enjoy it. Alpine bindings resist pressing, tweaking, and the loose, playful feel that park riding demands. If you occasionally hit small jumps and ride through the park casually, it's manageable. If you spend significant time on rails, jumps, and freestyle features, you'll find alpine bindings frustrating and potentially limiting your progression. Most riders who mix aggressive freeriding with park riding are better served by stiff all-mountain bindings (flex 7-8) as a compromise.