We wish, but we are poor.
If your invitation says "and guest" you are more than welcome to bring someone. If your invitation has your name only we would prefer just you.
Yes, if they are designated on your invitation. If not, we would prefer they did not attend.
We will have a host for the open mic who is organizing who plays when and how many songs each performer receives. The open mic won't start until all wedding formalities have concluded and dancing begins.