Hey mate. Firstly, congrats on the CPL. Big achievement. My first lot of advice is don't take what is said on here as gospel, and don't take it to heart. Pprune is, at its core, a toxic place. There are definitely helpful threads and people out there who are genuinely willing to help, but more often than not, it's people just looking to put someone down.
At any rate, here are some answers to your questions:
1. There is no answer to this one unfortunately. I think you know why, I don't really need to go in to it.
2. It depends on the company. Some require you to be "in location", I.e. if you're applying for Broome Aviation, you won't be able to be sitting in Sydney and hope to get a reply. You need to be there, working at a Coles and waiting for your shot. I do know of people who have done it online, without being there, but it was a very different time, and they're definitely the exception to the rule.
The application process depends on the company. Obviously CV/cover letter, some do phone interviews prior to an in person meeting. Nearly all will require a check in the aircraft or a synthetic trainer. Some even make you do a psychometric assessment as well, however I know that a few GA places that make you do this, basically ignore the results.
3. This is totally job specific and there isn't any hard and fast rule. Look at the job requirements.
4. Treat all interviews as a professional event. There's no such thing as a "GA interview". They're not as structured or as long as an airline, but you're still being assessed from the minute you walk in the door. The format will depend on the company. A mixture of: introductions, behavioural questions, tech/IFR questions, scenario based stuff. Again, there's no hard and fast rule and every company is different. If you've got a bit of experience in a particular aeroplane, they may ask you tech questions about that aeroplane. Yes, once again, some people get in by randomly meeting the CP at a bar, but they're the expections.
5. The company, your aircraft, their aircraft, their people, IFR (if applicable), general aviation knowledge, how to structure an answer to behavioural questions, have stories for behavioural questions.
6. Never done one for anything other than an airline, and to be honest, I don't think it would have helped me. I do know people who have done it for some of the "higher tier" GA jobs, like Hardy's.
My biggest piece of advice is to know your worth and absolutely do not sell your soul to fly that shiny new Caravan or Barron. You are worth the air pilot's award, or better. If you accept less than that, it is undercutting everyone else who will have to do the same because you're telling the employers that it's fine to do that.
It's a hard time to be in your position. There is absolutely no movement, especially with the number of stood down pilots with years' of experience currently working in supermarkets. Just keep at it, make yourself known to operators, and know that you will have to move.
Disclaimer: there will be people who disagree with me, that's fine. This is knowledge based on my experiences and I have tried to be as objective as possible. Let's all just try and keep it civil down below.