Yes. Each one is a testable question with something measurable, and the project workspace walks you through the write-up judges expect: question, hypothesis, variables, procedure, results and conclusion.
A research question and hypothesis, the independent and dependent variables, the variables to hold constant, a full materials list with costs, numbered steps, safety guidance and a data table you can fill in as you test.
It varies, so every project page states a cost estimate and a realistic time estimate up front. You can rule a project in or out before buying anything.
Some do. Every project lists its hazards and whether adult supervision is required in an at-a-glance panel on its page, so you can check suitability before you start.