Jet engines are designed to achieve their best specific fuel consumption at high rpm, which can only be achieved at high altitudes where the air density is low.

Thrust produced will be low enough to equal the required cruising thrust. Also high altitude gives the best operating conditions for the airframe i.e. minimum drag during the cruise.

Turboprops need relatively dense air for the propellers to work efficiently and at high altitude the density would be too low.

The Dry Operating Mass (DOM) is the Basic Empty Mass and the Variable Load, also called the Aircraft Prepared for Service (APS) weight.

The point during a flight at which an aircraft is no longer capable of returning to the airfield from which it took off due to fuel considerations.

Beyond this point the aircraft must proceed to some other destination.

They are aerodynamically efficient surfaces located at the wing tips, designed to reduce induced drag and increase fuel efficiency.

They increase efficiency by reducing the size of the wingtip vortices, which are created by the difference between the pressure on the upper surface of the wing and that on the lower surface.

No, VMCG is defined as the minimum control speed on the ground, with one engine inoperative (critical engine on two engine airplanes), takeoff power on other engine(s), using aerodynamic controls only for directional control and thus only applicable to ME aircraft.

A line of shortest distance between two points on a sphere.

Contingency fuel is carried to account for additional enroute fuel consumption caused by wind, routing changes or ATM: ATM/CNS restrictions.

No

Yes, the closer the C.G. is to the rear limit, the less tail down force is required, which means less drag which results in less fuel burn.