Do i have to be in the Business School to go into business?

No, a lot of managers start off as engineers, doctors, sales personal ... After a while, their performance show their uniqueness and climb up the ranks.

No, it's not a requirement. Like Wael said there are people in various professionals that are now in business areas due to different reasons (and some even decide to go to business schools after that). However, there are many benefits of attending business schools if you want to go into business. Some are:
1. It would help give you strong foundations/frameworks on various business areas (finance, marketing, supply chain, etc.) that you're interested in.
2. You will have access to alumni network of that school (which could be invaluable when you try to find a job.

The answer is no.
But a lot depends on your background, how far along you are in developing your idea, and where the market is for your product. If you’re working with co-founders, a lot will also depend on their expertise.
Going to business school will set you up with a very broad network of people who could be instrumental in the success of your startup idea.
And business schools also typically offer courses specifically geared towards entrepreneurs that help you with the ins and outs of funding.

No, not necessarly.

In order to start a business, you need to have an enterpreneurial Spirit, a good idea for a start up and a budget for the investment.
However, having a business background (studies) may help you a lot to shape your enterpreneur spirit, you can take courses dedicated to enterpreneurship and business management. which will help a lot as I said.
Going to college will also help you build a large network of people who could be instrumental in the success of your future business.