Yes, they do. My DD2 is 6yrs old - she went thru this phase just after Xmas. Only went on for a few weeks but it felt like forever. I couldn't reason with her, she lost all her manners, she was vile to me, vile to her sister, ok(ish) with her Dad, but if you dared to disagree with her or simply not do what she wanted doing RIGHT NOW she'd throw a tantrum.
In the end I just ignored her when she was like this. I checked with school and they said she was absolutely fine at school (fortunately) - but they did say that not only were they doing a lot of work in her year at school (Yr 1) and that their days were quite hectic but also remember she knows she had to be on good behaviour at school and obviously pushes her boundaries at home.
If your DD wants the paddling pool put up - get her to help you find it, blow it up, fill it but tell her whilst doing this that she has to play in it to justify all the work and if she doesn't it'll be put away for good.
I get fired with request after request....I simply say 'no' if I'm busy at the time, or I disagree with the request - yesterday for example she asked for her hair to be put in piggy tails, to go out on her scooter and for me to find her shorts to put on...all in the space of about 36 seconds. I told her she had to wait when I had the time to help her out and she did.
I often tell both my kids that all good things come to those who wait and if you really want something that much you'll wait for it and keep quiet and stop nagging!
It is an age-thing. Don't worry about it. I'm sure DD2 will have a stage like this again some time soon - I can remember my Mum saying that age 7 was a bit of a difficult age - no idea why but she's always said that.
Thank goodness DD2 is my youngest then!