I have a 9 year old and this behaviour started around 8 years old. She has become independent in what she wants to wear what she wants to eat what she wants to do ect

She has started talking back if we challenge her on something she just constantly shouts STOP if we tell her off the world has shattered and she storms to her room but she also cries about what I would class as random things.

She doesn't always know how the things she says can upset people.

Now this all sounds horrible but she is also a bright confident, caring and loving child and I absolutely adore her and she has so many other positives.

My point is your not alone I really think it is a stage they go through and don't always think considerately like adults do.

I posted something along the same lines last week (but got very little response)
My 8 yo daughter has what can only be described as mood swings, bouts of sadness (which don't last long) and can also backchat.
I've reconciled that it's an age related thing, she's possibly having some sort of hormone surge and she's become more aware of the world around her, hence giving some strong opinions!
They're still children ultimately, and still pushing boundaries as they do at toddler stage, reception stage etc.

Like I'm doing with my daughter, I'm occasionally taking a step back from intervention if she displays unkind/rude behavior (she'll learn!)
Enabling more appropriate choices and picking my battles wisely!

I've got a soon to be 8 year old boy who is the same. We are working on it as what is polite so say with the pizza we've said it polite to make sure his friends get a piece first and if their wasn't enough we would just cook more. I think it's that they are transitioning into a different age bracket so what they want and what we expect has changed but because of COVID they haven't really had the experiences to make it smooth.

We've introduced a chore chart (only little things like pick up glasses after breakfast or ensure the towels are brought downstairs) as he was getting quite demanding now he can earn what he wants the tantrums seem to have stopped.

Clothes wise no idea I'm debating writing a sign saying I dressed myself for his back

I posted a while back in another Topic about my 9 year old becoming moody, unco-operative etc and didn’t receive many helpful responses - most were along the lines of ‘my child’s nothing like that’.

But I then found lots of old threads, posters who were having a similar experience to me (and you OP).

You’re definitely not alone. There is a shift in behaviour and we are seeing physical changes in dd that suggest hormones are kicking in.

We are trying to ensure consistent boundaries, patience but not tolerating rude, unkind etc behaviour.

We are also trying to offer dd more independence gradually, if she can demonstrate she can be responsible.
Eg she can walk to school alone if she can show she can get herself ready for school on time independently, without us nagging her to hurry up every two mins.

If there are activities she wants to do then she needs to help with prep - eg making the picnic for a day out or prepping/tidying when baking etc. An activity that involves a sugary treat needs some physical activity too (eg a long walk for ice cream).

We try to include her in deciding what to do on holidays/weekends (to the extent practical). Eg on holiday we each chose two activities we wanted to do then all agreed we would do all the activities with a smile and without sulking.

Screen time is the big carrot and we try to keep it back until after dinner, as a reward for good behaviour. We also insist on some physical activity.

We’ve really noticed dd needs much more sleep, she is never up before us. This makes term time often the hardest as she is tired and grumpy. We don’t arrange things for any earlier than 11-12pm at the weekend and let her sleep in as late as she wants.

We have a similar 8yo.
I tend to highlight the grouchy behaviour (without telling her off) and just ask her if she needs some time away from us all to calm down. Just along the lines of 'X your tones not nice and your being mean to your sister... You can go to your room an have a few moments down time if you like? Come out for a cuddle when your feeling kinder'
Seems to work that we acknowledge she's being stroppy but showing her some understanding that it's not necessarily deliberate.

I have a 8.5 yo and sounds very much the same. It’s been a challenge over the summer but I expect things to be better once term starts and she has to be more polite to her friends and teachers rather than us!
I have taken to reading books about parenting and trying to change my own reactions and behaviour. A common theme is that despite the apparent increased independence and that they are growing up children of this age need to know they are loved and be connected with adults just as much as babies and toddlers. It enables the brain to work properly and then to deal with their strong emotions. They might not say or show that though.

also giving mine lots more responsibility over her own life. She does seem very happy if I ask her to eg make everyone’s lunch or do some hoovering. Definitely putting her in charge of getting her own school stuff ready and cleaning her shoes etc