I think they don't, they are kinda born with it in the proper size and it never grows, at least like human hair, it only get's proportionally bigger as the yukkuri grows, but it feels like if the yukkuri got bigger with a growth ray or something, instead of a typical growth.
So probably when they lose it, they are done, same way for accessories.
Depends on the interpretation. "Argue it Easy" has teeth being repairable. Probably a matter of giving the yukkuri enough to eat and time to recover. No go on accessories though.
The guy DID put that shitrisa's teeths back, but i doubt you can do the same with hair and braids, since the teeths were whole, you know with the root and stuff, instead of just "splintered" teeths or "broken" teeths.
I remember a strip where Anon said something about the accesory growing together with the yukkuris, so he could see if it was an adult or a koyukkuri. This kind of thing really confuses me, I'm still trying to learn about these easy manjus .-.
They do grow, but think of them as limbs, if you rip them out and shred them, they won't grow back.
Yeah maybe that's a better way to describe the hair, it may be hair but also works like limbs many times, so it won't grow back like the human's limbs.
Remember that yukkuri's healing is barely superficial skin based, and limited to nothing burnt, but loosing limbs, eyes, hair, etc. They won't grow them back, no matter how much sugar or orange juice you pump on them.