Yes, this is typically referred to as card in / free exit.
In the case of a power outage does the turnstile lock into a closed or freewheeling position – after any battery backup runs out?
The turnstile is configured at time of order to free egress and no entry (default) on power outage. it can also be set to no entry both ways or free spin in both directions. To answer your question properly. It depends on the configuration, once the battery back up has drained then the turnstile will go into the state that configured when built.
Yes. For outdoor use you would want a galvanized, powder coated over galvanized or stainless steel finish.