Looking for Schengen VISA suggestion

I'm a self employed software engineer working as a remote contractor for a Berlin based German company. My employer is organizing a company-wide meet for 4 days in April. I also need to visit there. I've got a few queries.

1. Which VISA should I apply for, Business, Tourist or any other?
2. I also intend to stay there for 4 more days apart from 4 days of my official visit (total 8 days) to explore the country. If it's going to be a business VISA, can I also travel using my business visa as a tourist to other places in Germany?
3. If I want to stay there a bit longer as a tourist to explore the city and the country, will I need the invite with the extended dates or can I have the invite with the official dates, book departure flight of 4 days later and can stay 4 more days as a tourist to learn more about the city?
4. If I am provided with the lodgings accommodations for the 4 days from company's end, will I need to pre-book my lodgings accommodations for the rest of the 4 days before applying for the VISA?

Thanks for sharing your expertise and experience.