According to their website, Manassas National Park is open year round, from sunrise to sunset every day. Entrance and parking is free! You should be able to walk freely around the park grounds, and there's a nice mini-museum at the welcome center. That said, there are no park events or activities scheduled for November on their calendar.
My understanding is the Battlefield is open but programs and ranger guided tours are not as frequent. Great visit and you get two battles for the price of won!
Yes the park is open year round.
Not sure. Check their website.
Thanks! Your answer is awaiting moderation.