The questions show ignorance of the subject.
What platform are you working on should not be a drop-down to choose 1, but in checkbox mode to choose several.
This is merely puzzling:
We, the (Android\Apple\ Windows 8) App developers, are different from developers of other platforms
App developers don't work on the OS, so this makes no sense:
I am willing to put in a great deal of effort in order to improve the (Android\Apple\ Windows 8) system
"The rest of my career"? Poorly worded, for a career is not the same as a time period:
I would be quite willing to spend the rest of my career developing for (Android\Apple\Windows 8)