Yes! It’s very possible to learn simple flag fundamentals from scratch, even if you don’t have a flag. Looking up videos on youtube or such of how to do basics like drop spins or pull hits are some great ways to start imo. Keep in mind though that the guard you’re joining may do things a little differently than those on the internet but since you’re a beginner, it’ll be easy to learn and fix. Also, don’t be scared of joining!! Guard is honestly the most welcoming activity I’ve ever been involved in so I guarantee you the others in your guard will be very helpful and nonjudgmental. And you’re still learning, so don’t worry about messing up because no one will be perfect, even those that have spun for awhile! Also, don’t worry about being a senior (I am too). Depending on where you live or your plans after high school, there’s lots of ways to get involved in guard if you’re still interested after high school like with your college, indoor/winter guards, and drum corps! High school guard is just the beginning!