I was going to say yes, no, yes, yes, but I can't do that.
Of all your question areas, I think the one that requires further discussion is a person who would protest and want to have his face covered because he knows that there may be a foreign government that will cause harm to his relatives in his home country. That's the value of lawful excuse. That would certainly get my attention and I doubt very much that somebody would be prosecuted. However, you waive that right once you actually participate in the riot. This is where the police discretion comes in. I can't imagine a woman with a religious covering or facial covering, first off, participating in a riot where they condone that. That would certainly fall into areas of discretion where we wouldn't prosecute, once again, unless they were involved in the riot itself.
I guess the issue I would make is that we all make choices in our lives. I choose to be at a riot. I choose to participate. I choose not to go home when things start to turn ugly. We are all responsible for our conduct and our actions. I think choices have to be made by people who attend these kinds of events. I'll let it go at that.
The majority of your questions would want to be addressed by a legal scholar or a crown prosecutor.