I think you will understand if I don't give new techniques to how to steal a bike. I think there is enough advices available on internet to help thiefs to steal a bike.

Regarding the second point. The strength of an angle grinder is its teeth on the disk but those teeth are also its main weakness.
What happen when you rotate your fork in a bunch of noddles? It stick to it.
The same things happen when the rotating part of a vacuum cleaner meet long hairs. Hairs get stucked.
How long that it takes to remove those hairs stucked... a while.

With the right wires placed in the right way on an ulock or a chain, these wires will stop the rotating disk of the angle grinder from moving.
In fact there is more than one solution for the angle grinder problem.