Personally, I don't think it will hurt the battery. Plus newer models have pre calibrated batteries that you don't need to calibrate. I keep mine plugged in whenever I play video games because the discrete GPU is a battery hog.
It's commonly said that using outlet power when your battery is 100% shortens its lifespan. If you want a clear answer, I'd do some research on lithium-polymer batteries.
Its fine to use your MBP whilst fully charged and running off the mains adaptor. Just pull out the magsafe when you're not using your MBP. Its pretty safe if you forget but just don't go on a 2-week break leaving it plugged in at home.
No, it won't be a problem, as long as you don't run on AC power all the time. Your battery needs to be used periodically to maximize its lifespan. Read the AC POWER section of the following FAQ.
This should answer most, if not all, of your battery questions:
That's only true if you leave it plugged in all the time. As long as you periodically use the battery power, it's perfectly fine to run plugged in most of the time.