Are you required to cross the finish line on a bike? Suppose you get a flat 100m-1km (or some distance that you can sprint/run) from the finish line. Can you leave your bike and run the remaining distance to the finish line? Or are you required to carry your bike while running? Or are you required to cycle across the finish line (i.e. wait for a service car to come fix your bike)?
UCI regulation 1.2.109:


  The rider may cross the finish line on foot, provided that has his bicycle with him.


Note that "his bicycle" may be a teammate's bike or a neutral service bike (and that "he" may be of any gender but the UCI are too lazy to rewrite their rules).