E-Business Suite 12.2 Online Patching

I am just starting to look at documentation for 12.2 upgrade. I have a few questions about it.

• When you 'cutover', does the url:port the customer uses have to change? (particularly the port number). I understand each app tier has its own set of ports.
• What is the 80gb of clone space in the app tier needed for?
• Documentation states that 'development' servers only require 1 tier. I thought two tiers were required.
• Documentation states the adop can be used to apply several patches at a time. What about special instructions in patches? It would seem that one would rarely be able to run several at a time.