See if i can shed some light for you.
1. Can't help there.
2. Varies as to what type of aircraft (GA vs airliner etc) but roughly it is as follows: -
Always:- nav lights (red and green on wingtips), anti-collision strobe (usually red - can be white on some US built military aircraft)
Taxi: add taxi lights
Takeoff and landing: add taxi lights and landing lights, wingtip white strobes
Cruise and Descent: nav, anti-coll and wingtip white strobes only
I believe some airliners turn on the inboard wing landing lights on descent aswell.
A lot of GA operators will leave their landing lights on for added visibility all the time when airborne (ie in high density training areas etc).
At night, some large aircraft and military aircraft will not turn on the landing lights until late on finals, as this can actually cause disorientation to other aircraft in the circuit.
3. Yes, to an extent. Usually low performance GA traffic at night, as any high performance aircraft will separate itself vertically or laterally as they will generally be IFR.
4. Yes, lighties generally only have one landing light (no taxi lights), anti-coll and nav lights (no wingtip strobes, generally).
Large aircraft can have a number of sets of landing lights (inboard wing, outboard wing, wingtips, main gear and nose gear) etc, with some being retractable and some being fixed in the wing root etc.