1. As many times as you want.
2. 300 is quoted sometimes, I'm into a pr well over 100, but don't really know
3. C is a discharge rating and is also used to spec charging. A 2S 5000mah 30C lipo is able to produce a continuous discharge of 5000/1000 x 30 = 150amps. An 8000 15C lipo would be able to discharge 8000/1000 x 15 = 120amps. Its a function of the C rating and the capacity of the lipo. Its alos used in chargibng - a 1C charge for the 1st example above would be 5000/1000 = 5amps. A 2C would be 5000/1000 x 2 = 10amps. A 3C charge rate would be 5000/1000 x 3 = 15amps. Lipo manufacturers will tell you (usually on label) what they advice for charging. If not specified, stick with
1C.
4. A 5000mah with 20 - 30C would be a long lasting lipo with plenty of punch.
5. I'll check, theres a good one on a heli site and i'll have to find it. Here it is found it -
http://www.rchelicopterfun.com/rc-lipo-batteries.html