The rope has nothing to do with starting the engine. As bizarre as it sounds, it's supposed to be tied to the engine and then a hard point on the transom in case the engine falls off

As to a TLDI needing a battery, absolutley true. While the engine will start without a battery or one that lacks sufficent CCA's, the ignition system will NOT energize correctly and it will not operate correctly. This holds true for the Mercury and Yamaha models as well. However, the Evinrude DFI models can start and run without a battery.