Interesting to see the different responses. I live in a country where children aged 6 regularly cycle themselves to school so this does influence some of my responses.
have a tablet - eldest had one bought for him aged 4 🤬 my preference would be around 8 for educational games etc and with strong parental controls.
have a phone - eldest is 10 and I'm considering getting one now as he cycles between friends houses in the warmer months and they go off for bike rides in the area (lots of cycle paths)
play date without you staying - from age 4/5. Middle child aged 7 likes me stay until she's comfortable eldest waved me off at the door.
go outside to play without supervision - our own garden from age 2/3 with me being able to check from the window/being close by. On our quiet cul-de-sac aged 3 with older siblings and with me checking on them often. Aged 6/7 otherwise.
cross the road - eldest was crossing a road with lights aged 6. Middle child is 7 and hasn't done so yet. Would need to do some training before letting her.
have a sleepover - eldest was 6. Middle child (7) hasn't yet but isn't fully comfortable with play dates at other people's homes.
Fully bath/shower themselves - fully unsupervised probably from age 6/7. Need checks on teeth though.
go downstairs in the morning without you getting up - we don't have a downstairs (!) but they're up and watching tv before me on the weekends. They know where to find me if they need something. I'm only a few paces away if the arguments start!
make their own breakfast - youngest (3) can make her own cereal and has done from age 2. She's seen the older ones make toast so can do that with supervision. Eldest I showed how to use the microwave, make noodles/pasta and turn the oven on age 9. With the rule he has to tell me if he's making something in the kitchen.