For #3 that's not strictly true - while the policy doesn't discriminate by vendor, it does discriminate by content type and by packet sniffing capabilities. For example, unlimited video uses the same bandwidth as a VPN downloading at the same speed as the video's bitrate, and are equal from a network management perspective - but they get vastly different treatment towards your data cap.
Given a scenario, ask the following:
"If enforced, will this give the users a financial incentive to pick one information source on the Net over another to get the same content?"
If the answer is YES, then the scenario is a violation of net neutrality principles.
So for the 4 scenarios you listed, the answers would be YES, YES, LIKELY NOT, and NO*
(*only because we restrict the test to sources on the Net).