I am in 10th grade. So, yes, enjoy the fact you are a kid. You don't have to drive, pay anything, and practically get free rent! Don't rush your youth, but if you really want to do adult things, I suggest you talk to your 'rents about it. Your sister is not favored, but she is older and therefore is given more responsibility. I understand your pain but enjoy your childhood, you'll miss it when it' s gone.
It makes me a bit sad that you want to rush into being an adult. I'm an older teen and I know what it's like. Listen. And ditto to everyone else. And responses to your gripes about your sister:
1. She gets more attention? I doubt that. She probably doesn't like you getting babied and possibly even doesn't like babysitting cuz she cant do what she likes.
2. Who cares where your clothes come from!?! Mine come from places like Old Navy and Wal-Mart. And did you think that maybe she's spending her own money that she earned? If not, then maybe you should ask your 'rents if you can too. Also, little kids and preteens grow a lot quicker and then your 'rents have to spend a lot more money to get you clothes that fit you.
3. She is not loved more. Parents shouldn't have favorites. You are loved if they want to protect you. As you get older you will get the same privileges. And I bet she was just like you when she was your age. All good things come to those who wait, so be patient and enjoy your youth! (I even wish I could be a kid again.)
I hope this helps. Live your life slowly cuz you'll never get it back!