Mind the time 🙃I've had a cousins wedding this week, so been keeping some crazy hours.
Modesty standards in Orthodox Jewry varies massively, some will wear longer skirts, some shorter, some will wear tights, some won't, some cover elbows, collarbone etc. A modern orthodox women would be a lot more relaxed with her modesty, and ultra orthodox would be more stringent.
Largely, the expectation is that you follow your family and local community's custom.
These customs vary, for example, one of the most conservative and traditional stream of ultra-orthodox Jewry is in Stamford Hill. There are some Ultra orthodox chassidim who are exceedingly stringent with modesty and very possibly they ensure their 3 year olds adhere to modesty standards like you described. Many Chassidim who are very particular about modesty would be careful not to lower their standards even at home. This can mean no taking of socks/tights at home (only in bedroom), wearing night dresses instead of PJs, Swim-dresses instead of swimming costumes etc.
Personally (I fall under the ultra orthodox community, although not chassidish) I dress by the guidelines of covering from my collar bone (think crew neck jumpers) until my elbows, and a skirt/dress to my knees. I also wear tights when outside. And obviously my wig.
At home I wear PJs/leggings. I'd walk around at home without tights np, although I'd keep a skirt on.
Since having kids I make sure I'm modestly covered around them. This isn't a must, rather its a sensitivity I've decided to take on. So all my Pjs are long sleeve and trousers. I'm careful to cover my hair with a scarf at home around my kids.
But in my bedroom, when the door locks, everything comes off 😊