I think we worry about activities such as a science fair because you have to explain your findings and showcase your work. It can be hard if you are a shy person. This is why it's very important to be prepared. Make sure you have researched your topic using multiple sources. Also, it's beneficial to show the process you went through using the scientific method. While doing this, have plenty of visuals on your table and be ready to back up your answer.
As far as answering your own question, you absolutely want to do that. The third step of the scientific method is to "form a hypothesis" which is to give an educated guess on what you think the outcome will be. The final step is to indeed answer your own question.
Here are the steps of the scientific method to help you out:
1. Set the purpose for the experiment (question you want to answer)
2. Research using multiple sources
3. Form a hypothesis (educated guess)
4. Do an experiment to try to find your answer
5. Analyze results and make changes if necessary
6. Conclude your final results
7. Communicate your final results (which you would do at the science fair)
See the link below for more information on the scientific method. Good luck on your project!