It sounds like homework because the answers are valuable to study yourself, but near-worthless as a result.
But since you are declaring that they really aren't homework:
1. The relationship is complex. As you wrote, it depends on the complexity of the project. In simple terms, you can estimate projects and their budget in FTE Years, or number of years for full-time employment. A 100 FTE project with 50 full-time workers will take two years. A 100 FTE project with 20 workers will take 5 years. A 1 FTE hobby project with an individual hobby developer may take 5 years. But in practice work isn't directly transferrable, it depends a lot on the person doing it. As a parallel, you can say it takes about 100 people to construct a new house, but it's stupid to hire 100 electricians and assume that your house will be built just because electricians are involved in building them. You'll need to dig in to comparing projects, read post mortems, and look at games credits to get more than that.
2. It's the project, not the genre. Go read project post-mortems, both successes and failures.
3. Why is work hard? Why is research and novel development hard? No matter how brilliant you are, it is difficult to predict how long it will take to invent something. Project managers do a tremendous amount of work to minimize risk and work complexity, but it is never eliminated. Go read project post-mortems for more.
4. It takes what it takes. AAA games are the only ones with a realistic answer, since AAA has a meaning of the highest budget premium games. For those, expect a main development budget of at least $0.1B dollars and potentially double or triple that, and about the same in marketing, and about the same in other costs. Less than that may be big, high quality games, but aren't going to be today's AAA.
5. Google it, but these really are bad questions.
6A. When they have done it for a while.
6B. You don't. You can compare results to other people's results, but it must be taken with a grain of salt as everyone's skill set is unique. Two people given the exact same task will come up with different results, given a task someone may even struggle and fail while still being an amazing developer. How do you think you would compare a gameplay programmer's skill, a graphics programmer's skill, a network programmer's skill, and a tool programmer's skill? What do you think would happen if you tossed the jobs around, gave a graphics programmer the network programmer's tasks, gave the tool programmer the networking tasks, etc? Those are also great research topics for anyone hoping to manage technical workers.
6C. It should have the skill sets you need. If you have a team of 10 people but all ten are amazing graphics programmers your game is going to suck.
The answers may sound rough or not what you'd like, but I'm quite serious when I write that the value to questions like those is not the answer, it is the benefit of researching it yourself and the things you learn along the way. That's why they are really good academic questions. Those answers should be enough for search terms to dig deeper.
