Yes, you need Composer in installing Magento 2. Composer is a PHP package manager similar in concept to Maven for Java developers. It is a tool for dependent management in PHP which allows you to declare the dependent libraries your project needs and install them for you. Composer enables you to manage Magento 2, extensions, and their dependencies.
And you must need MySQL 5.6 or above in order to work with Magento 2.
If you are working on a project for a client, I would recommend you to go for Magento 22.214.171.124, which is the latest stable Community version available at the moment.
But you can play around with Magento 2 and get an idea on the existing release so far on GitHub.