4. You can try to "stumble backwards" at first: When you loose balance backwards, you can compensate by hopping the rear end of the bike backwards a bit, mostly by bending your knees. From that "stumbling", you can try to move to an upwards jump, keeping the bike a bit more in place and in balance. Soon you will notice that the pedals will move backwards with each hop, making further hops impossible after a few hops. Therefore, you learn to open the brake a bit. Thereby, you can compensate your jumping motion by moving the pedals a bit forward. When you can do that, try to do little forward jumps, by pedaling a bit more. Don't jump off edges unless you can control the move quite easily on flat.
5. Neck roughly above handlebars, bend your arms to lower the upper body towards the handlebars, then straighten your arms relatively fast and with force and push the front end of the bike forward and upward in a rather circular motion (at least in your mind). Your body should move backwards, relative to the bike. Knees are bend a bit the whole time, you can bend a bit more while pushing the bike through, it helps with the jump: You need to find the right amount of force and motion, so that you can comfortably counter the rolling motion by jumping upwards "towards the handlebars", when the front wheel is high enough in the air. A bit of the jumping comes from the arms using the handlebar, but most is in the hips going towards the handlebar and the legs pushing against the pedals. Beware of losing pedal contact.
6. Yes. Just use 5 with less force and compensate by pedaling, but not with very much pedaling force. Focus on the jump, not the pedal kick.
A gap jump from a standstill is an advanced move, worth years of training. You need to have a stable backwheel hop for this. It should feel a bit like a jump without a bike. Therefore, you turn your bike sideways a bit, so that your feet are placed more naturally side by side on the edge of the gap. Most importantly, don't kick the pedals actively, this is a common mistake. The pedal move just compensates for the jumping movement, a bit more than that, but not much. No hard kicking is necessary for me to gap 8 feet, and I don't think the pros do that when they gap 11 feet.