Club Level amenities, including food service are for club level guests only. Some people have reported asking CMs to have a guest for a specific service time, I have no personal experience with that. If it’s just you in your room or you have capacity in your room for an extra guest, you could add that person to your reservation. Just ask for a key card for them to access the club level. Then they could stay in their own room but still accompany you to the lounge.
Not unless they are on your reservation. Otherwise everyone would book one club room and then invite their friends. The club level lounge is just for those paying for the privilege.