No – you’ll be fine. It’s a great age to start strength training. I just started training my 13 year old daughter who plays volleyball and softball. However, as others have pointed out, it’s very important that you learn how to do all the exercises correctly. Start out light and don’t worry about how much weight you’re using – concentrate on using good form. If you don’t, you probably will end up getting hurt so let’s not do that.
The strength gains will come but you need to be patient. Also, you’ll need the help of a personal trainer or a Phys. Ed. teacher at school to make up a workout plan and supervise you to make sure you’re doing the exercises right – that’s important. Using dumbbells are fine & body weight exercises are great too. You’ll probably need different weights for different exercises – some muscles are stronger than others. Start by getting help from a qualified trainer or ask at school – I’m not crazy about a few of those exercises you mentioned – especially wrist lifts. Good luck Kaden & have fun with it – that was the age I started! Check back & let us know how you’re doing.