Teddyburr

I got my kitten, and her siblings, when they were very young. They looked like their eyes had just opened a couple of days before we got them. She's about 8 now, and doing great. But i was wondering why it is bad to get kittens early? Like is it behavioural, mental, physical? I wouldn't ever buy a unweaned kitten or anything, i'm just curious what the reason is.

Also, I don't want anyone raving about how we shouldn't have gotten them that young, we found them under a shop. There was a dead cat down the street from there, and we figured that was the mom. We had an older cat at the time that i figure taught her boundaries. Also we only kept one, the other two are still alive and apparently normal, we found homes for them.

My bird keeps rocking from side to side, and i do it back because i think it's adorable. But i was wondering if that was aggressive behaviour? It seems like he's just happy and playing but i want to make sure im not repeating a bad behaviour.

And also i have him in a very large cage, like the big metal ones, and do you know where i could buy seperate parts from cheaply? A wheel broke.

With the big cage he's got toys that fall under the grate(i think that's what it's called), like balls, bottlecaps, and a few plastic toys that he drops from the top. Is there a way i can keep him from going under? Because he doesn't know how to get out and he panics and i'm scared that he'll hurt a wing or something on the grate.

Any help would be welcome, thanks!