OEM Lock questions

We are looking into the OEM Lock solution, but have a couple questions:

Scenario #1: A project is partially developed on one gateway with a license, or running in trial mode. Then moved to another gateway with a different license.
Question#1: Can this project still be OEM locked?

Question#2: How difficult is it for the OEM to work on the project if it’s locked? I.e. - would we have to swap licenses back and forth, or can we simply load the key license, make modifications, then remove the key?

Question #3: A project is built on the gateway with the license for the OEM Lock, and the project is installed at a customer’s and locked. How difficult is it to unlock, and keep unlocked, a project without leaving our OEM key on the gateway?