What programming language is the best to develop in?
Again, no best answer. The level of documentation depends on each language. Actionscript 3 is a well-documented, easy to learn language (quick results), but it is slower to run. Most examples are written in flash, giving you a larger sample to learn from. C++ is harder to code for, but will give you faster programs. Python, Java and C# (WPF) are also options.