I am a highschool student in Washington state. I have much experience in business/marketing. I am starting my own clothing brand as a new venture. I have several legal things I would love to get some feedback on.

1. From everything I have read, I need to trademark the name for my brand. The trademark is available, so I am assuming this is my first step.

2. I have 10 tshirt designs. 9 of them have a custom design above the name of my brand. 1 of them is my logo, with the design to the left of the name. What do I need to do in order to protect my name and designs?

3. I am assuming I should form an LLC for my clothing company, or should I form another kind of business structure?

4. Once I trademark the name, how do I show that it is trademarked? Do I add ® next to anything that says my brand name?

Thanks in advance! I would love any feedback you guys can give!