I was wondering could I complete offers under one address but have my order sent to another,because the terms don't really cover it.
Unfortunately, rewards may not be sent to 3rd parties. It would need to be sent directly to you.
It's my address but I signed up a while ago and now have new address,but some offers were done under the old address so do I update my account to the new one and finish or keep the old one.
Submit a support ticket and they will be able to sort it out for you.