Yes, the tail feathers will grow back. As long as the root of the feather where it emerges from the skin wasn't damaged, it'll return when nature continues his molt. Look for signs of new growth in the next few weeks. It'll look like a tight straw poking through - it'll be plastic looking and whitish. Let him break the sheath and release the feather inside since these are especially sensitive.
Hi, yes flight feathers will grow back. Tail or Wings. Obi had his wings clipped when I got him at 2 months and it took him a year to grow his flight feathers back at his first molt. It helps if they have had a bit of flying practice before the wings were clipped otherwise they can be a bit clumsy.
Here is another link for you that I found very helpful when I first got Obi
Ollies feather were clipped by the breader when first brought.
If you speak to a vet about it, they'll question why it was done and not recommend doing it again.
The breast plate and muscles won't be full grown at 6 months.
The risk of damage to the bird is increased by clipping early....
Yet breaders do this ? Either to protect us as new owners from loss or protect the bird on a new home.