I made the mistake of nagging endlessly when one of mine couldn't be bothered to bring her laundry downstairs, but one day I just stopped doing any washing that wasn't downstairs by the wm on a Friday evening, and she still didn't do it, so she washes her own clothes now instead. Make it her decision if she wants her clothes washed for her or not.
I think you are right to worry about Snapchat tbh! If other parents aren't bothered that's down to them. But if you want to spot check/ monitor it then go ahead and don't be apologetic about it. You are paying the phone bill.
With the phone we had daily time trackers which they had to show us randomly and keep at a reasonable level during term time (you need to decide as a family what you think is a reasonable number of hours a day). If they still wanted a phone contract they had to comply with the "reasonable" hours we all set. We adjusted the hours as they got older and weren't too ruthless about it as it's better if they learn to self regulate. (Keep in mind that teens use phones to maintain friendships, listen to music, as dictionaries & calculators, as alarm clocks (although we had the usual kind!) and calendars, to play games, when my generation had all of those items in stand alone form.) On school/work nights the phones went in phone lock boxes from Amazon and were left downstairs overnight (and that applied to whole family). Different now they are over eighteen obviously!
For weekly chores, I eased off over exam periods but for the rest of the time, we expected them both to empty the dw when they came in from school while having their snack and walk and feed the dogs in the evening on a rota three days a week each, and join in family bed making on a Sunday. Not a lot of chores. Again, don't get drawn in to arguments. If they don't do them, they don't get the earned part of their allowance. We made half of their allowance not contingent on chores and half earned. Again, no arguments, make it their decision if they want the earned half.
As for general backchat and hating everything and being rude to you, I would honestly say, step back, walk away, don't engage and do not let arguments get in the way of your relationship. I made the mistake of getting in to a negative spiral of disagreements with one of mine and it doesn't help anything. Half the time they don't realise they are being rude and you have to wait until their frontal cortex joins up with their limbic system (at about 24 years of age) for them to get full self awareness. It's good to use humour to defuse tense situations.
Ultimately, it's the quality of their relationship with you, and your closeness, which will largely determine whether they go completely off the rails or not when they are older and you no longer have the same control over them. And your relationship is the most important thing for their self esteem above everything else. Above all, they need to feel that they are loved for themselves unconditionally even when they are being brattish. Actually when they are being the most brattish is probably when they need love the most.
Tell her often that you love her as the teen default mode seems to be to think everyone is against them. And show her you love her in small practical ways like picking up her favourite snack, taking her out for a 'grownup' coffee or lunch, going to the cinema together etc.
So basically treat her like you would a grown up version of a toddler; eg engage with the good and ignore the bad. Physically leave the room if you have to. I have left the house on occasion! Keep the lines of communication going and let it know you are available at any time if they want to talk or have a problem or need help, but make it clear you will not engage with them while they speak to you like rubbish. Always keep calm and give yourself time to think. Don't be pressured in to making decisions quickly about a party or an overnight stay. Tell them you will "think about it and get back to them". If it gets really bad, just calmly tell them that you won't be spoken to like that and withdraw.
I always take bolshiness and "superiority" as an indication that they are ready for more responsibility (a bit like when an infant outgrows their high chair and starts protesting and arching their back it's an indication it's time to sit at the table in a proper chair). So try giving your dd some tasks that stretch her a bit, make her a bit uncertain, involving a journey or a "mission" of some kind, where she has to solve a problem outside of her comfort zone. The DofE award scheme is good for that. Encourages a bit of humility and appreciation and an awareness that they don't know everything yet! If your DD is competitive, give her a challenge.
Read 'Untangled' by Lisa Damour which is often recommended here on the teen girl threads. Your daughter's behaviour is telling you something. She is starting to split herself off from you in order to become a fully formed adult in her own right. This is a normal process but it's hard on them and on us.
Go with the process and step back a bit and don't get involved in the minutiae whole supporting from the sidelines. Be busy with your own life and projects. Model common sense, cheerfulness, self care, resolving problems in a calm reasonable way, model enjoying yourself and getting the balance of hard work and leisure right. She may not be talking to you but she will be watching.
Get some support for yourself if you need it. Don't allow yourself (as I did) to be mentally worn down by the emotional ups and downs of your teen. Step back a bit. They need you to be solid and strong while they are all over the place!
Start each day afresh. Don't let arguments run over in to the next day or spoil a birthday or outing or holiday. Refresh and start again.
And just hang in there! It can be a bit hellish but she will come out the other side I promise! (Both of mine are starting to "come back" now although we still have our moments!) Good luck and sorry for the long essay! Thanks to one of mine being "quite challenging"
this is my specialist subject ATM. And I made a hell of a lot of mistakes I wish I hadn't first time around.