I managed to get the 777 running in P3D v2.1 using the Estonia Migrator Tool and running P3D in Legacy Mode. The aircraft does power up but some things are not working. I am unable to start the engines other than using Ctrl + E. Manual starts just do not seem to work. I am also unable to select the majority of the lighting options in the aircraft such as the panel lights and most external lights. When running P3D in error logging mode, there are multiple gauge errors for almost all the lights. Only using the "L" key seems to turn everything on, but the switches in the cockpit simply do not work. Even if they move they are non-functional. It is not possible to control the lighting individually, except for the taxi and landing lights, using the "L" key is a all or nothing deal. Some lighting knobs will not move at all, even though the mouse cursor changes to the hand cursor when hovered over the knob. They did rotate in P3D v1.4.

I believe that this is one Captain Sim aircraft that is a bust for use in P3D v2.1.  :-/