I addition to what Peter Kämpf has written, regarding point 1. If I unterstand the things correctly a plane needs generally a thrust-to-weight-ratio above 1.0 to be able to fly vertical. Planes are generally below 1.0 because their wings generate enough lift during flight and more powerful engines would be ineffective. For example the 747 is around 0.27 and as Peter Kämpf noted, VTOL capability would require 12 additional engines.
https://en.wikipedia.org/wiki/Thrust-to-weight_ratio
Some fighter jets have more than 1.0 which are, for example, the Typhoon or the F-15. They shall be superior over others and so efficiency is defined different. And of course also the Harrier, not designed as superior fighter, but it must operate as VTOL aircraft. While not listed, I think the V-22 also must be above 1.0 ratio. Interestingly, the F-35 is with full fuell tanks far below 1.0 but it is a STOVL aircraft, not VTOL.