2. You can buy day passes at specific vending machines at both airports.

3. Many opportunities, mostly just outside downtown. Some of my favorites:
- Brown Line between Clark/Lake and Armitage (best!)
- The entire Loop elevated in its "skyscraper canyon"
- Orange Line between Adams and Halsted
- Pink Line between Clark/Lake and Polk

The station with the best view may be Cermak-Chinatown. If you get a chance, board the last car and walk to the very end to the empty motorman's cab. The skyline views from this seat, as the train speeds out of downtown on any of the Loop lines, is awesome.

Needless to say, you'll get the best chance to savor views if riding outside rush hour.