Bicycle left outside for over a year. Possible to save?
You don't have pictures of the bike, but honestly, theres not much you need to worry about. Pump up the tires and make sure they hold air. Check that the brakes work (may need new pads, cables). Add a new chain and you're likely good to go. 

A lot of bikes live outside their whole lives (in rain and snow) and aren't worse for the wear.