questions about transitioning to unity 5

1: do I need to uninstall unity 4 before I download and install 5?

2: can I keep both versions in case too much work is required for my project to properly work in unity 5?

3: if I decide I don’t like unity 5 will my project open up without problems if I reinstall unity 4?

  1. No, 2. Yes, 3. No.