The shop opens at 9am. (opens = verb)
The shop is open from 9am to 5pm. (open = adjective)
The department opens at 1pm. (opens = verb)
The department is open between 1pm and 5pm. (open = adjective)
Yes, it would actually me more natural to say "make/lodge a complaint" than to say "file a grievance". In BrE, it would also be more likely to be called a "complaints department".
Student or Learner