FALSE. If you really need a GPS your dependence on it could be your undoing. Any number of reasons could prevent it from working from battery failure to theft. A GPS should be used in conjunction with a compass and decent map.
FALSE. Naturally spanner size is critical but will the physical access restrictions of your particular bike allow it to loosen the plug? Check your tools before leaving home!
FALSE. The more you open your jacket the more it inflates and acts like a sail. This can be dangerous in a cross wind. In very hot, dry conditions this can also speed up dehydration which can cause you bigger problems than merely being hot!