View invoices and other

I have so many questions!

1. how can I view invoices that I have sent?
   2. Am I right in thinking that if I use bank explain, then this doesn't automatically record who has settled their invoice?
   3. But if I raise an invoice as well as use bank explain, would that record the payment twice?
   4. Almost all of my customers are invoiced for the same amount on the same day. Don't suppose there is a way to do them all at once, not each one manually?
   5. On the 'reports' page I can see the reports but the download as csv/pdf button is greyed out. Why would that be? Thank you very much!