If a show starts at 7 but the main person doesnt go on until 9 could I show up at 830 instead of when doors open? I rather just see the person.

Like Daniel said, you can show up any time, even after the main show has started if you're into being super late.

You can show up whenever you want if you pay for a ticket.

I have already bought tickets being it for tonight's sold out show just wont be there until 830

For the show I went to yes. I imagine if it sold out you couldnt.