I don't do custom border collies (apart from the occasional gift art), but I will do custom wolves and cats
over here. That shop is usually closed though - right now it's only open for candy, and even that's just for specific linearts (the young animals and the headshots). The only exceptions are for the custom anthros, which are for July/August wishlist pets only, and commissions that are being paid for with one of my 3- or 4-token wishlist dogs, either of which I'll take on at any time.
As for growables, that's more time and work than I'm willing to put into these guys - they're my little side-hobby more than anything. Some of the pups will eventually get adult versions, and I'm debating retiring the older adults and puppies once they hit a certain age. I'll probably have to, because with just the adults I have up right now, there are
124 different puppies they can have. o.O With the pups growing up and breeding, too, I would soon be overrun if I didn't start retiring them. That's also why I won't be making adult versions for all of them, which growables would require.

Puppies will probably either grow up or go to a non-breeding home (i.e. be retired) after one or two months - the codes will still work though, so don't worry that your puppy will disappear!