What do you mean? Do you want to read the build number on runtime? There is a way to do that, when you put them in the plist, just run [[NSBundle mainBundle] infoDictionary][@"CFBundleVersion"] to get the NSString.
Say I have 3 iPads in the office, and I want to load a build on each of them. I know I can use Testflight or similiar, but the easiest is to just plug them into my computer and press the play button. If I do that, it increments the build number, so iPad #1 gets build 4031, iPad #2 gets build 4032, etc.
No it doesn't, if you ensure it will run only on "Release".
When you deploy an app to a device via Xcode, unless you specify differently, it will compile in "Debug", so that won't cause an increment. Every iPad will have the same build.