You are not a citizen until you are sworn in. If you are denied because of failure to pass the English or the civics test, you will be automatically rescheduled within 90 days. If you are not approved for some other reason, you may be given time to overcome the problem.
For 2009, the American Opportunity Credit--which is a variation of the Hope Credit--will be allowed for 4 years. For years before and after the new credit is allowed, the Hope credit is supposed to be for 2 years.
No. Non-resident aliens cannot claim the HOPE or Tuition Tax Credit or the Earned Income Credit. Once you qualify to file as a resident alien for tax purposes, you may be eligible to claim these credits.