[Noob Questions] Help on building my first quad Arducopter


After roaming and lurking the web reading forums, blogs and watching videos, i have come here (looks like most active and helpfull UAV forum ive seen) looking for some … mmmm … “initial advice” on something i have in mind, lets go to it.

For quite some time ive been thinking on buying a drone, but recently i have change my mind, i would much more prefer to build (or at the very least try) one, i couldnt say what atracts me more, the idea of building it or flying it, maybe building it XDDDD

So, i would like to start with something simple, but buying the core components scaled so that i could later salvage them for my true objective. When i talk about “core components” i mean the RC controller, the receiver, the APM, the video emitter/reciver, … other things like motros, ESC, propellers, … should be specific for every drone.

My “true objective” is to build an UAV able to:
a) fly manned and/or by GPS path for at least 15-20 mins
b) be able to carry itself and an additional 1.5-2 Kg of load (additional equipment)
c) be able to operate on 1000-1500m distance of the base station while transmiting real time video

So now to the questions:

1) Whats the difference between APM, PX4 and Pixhawk? is one of them better than the others?

2) Would something like this make the same function? if not, why?

3) For my starter i have really like this one, what do you think?

4) As for the controller, i have seen this Radiolink AT-9, is it decent enough for my “true objective” project? if not, what would be a decent AND CHEAP one?

5) Whats the usual maximum distance at which we can get the video feed from on board camera?

6) Does the APM include sensors like altitude (barometric??), speed, magnetometer, gyroscope … or should i include them as needed? are those even needed having a GPS? maybe gyroscope for stabilization, yeah that should be a must but i dont usually see any sensor in “do it yourself” kits, why?

7) Will i ever be able to build my “true objective”? or suach a huge extra carry capacity is absurd? if not, what would be a good frame? (i prefer quads over hexas)

ufffff i have a gazillion more questions, but guess many will be self answered as i keep reading info.

Thx a lot for reading and 2x for replying XDDDDD, and my apologies if my questions are … well, noob questions.