Stall warning, stick shaker, stick pusher, etc...

Generically we can destinguish between systems that alert the pilot of the impeding stall, like stall the stall warning or stick shaker, and systems that try to correct the situation, like a stick pusher.

A swept wing makes the velocity vector normal to the leading edge a shorter distance than the chordwise resultant.

A wing tip is the part of the wing that is the most distant from the fuselage of a fixed-wing aircraft.

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.

8.000ft

Swept wings, thin wings.

A variable pitch propeller provides an optimum angle of attack for the propeller blades for a longer range which reduces fuel usage. Fixed pitch propellers are easier to produce and maintain, but reach maximum efficient at only one specific airspeed.

Decreasing speed, by reducing engine power or pitching up.

Mostly in the fan, but also from the exhaust nozzle duct.

To increase the strength of the surfaces.

The same strategy is employed by plastic water bottles, by adding ridges to a surface you increase it's structural rigidity