Plenty of things I need help with!

This might be a lengthy post so, I'll split them into sections. 

-Baby mobs-

I have read countless tutorials and have spent many hours attempting to look for a way a custom mob can spawn a baby version of itself when bred. From what I've gathered, this is not possible unless actual java code is implemented. I've tried many different ways with procedures, and while they produce the effect I want, they look rather unnatural. (spawning the adult mob first before spawning the baby one, a very noticeable visual quirk) so my question is, is there a way to implement java code into the mod with Mcreator, as well as what is the code and where would I put it? or if there's any other way to do it and make it look natural, please share your tips and thoughts! I have a model for the adult mob, and the baby mob, both implemented as entities within the game. If this truly isn't possible, I hope it is in the future!

-Tamed mobs-

How would I go about making a tamed mob sit down? Right clicking a tamed mob in game doesn't prompt it to sit, or even stand still, it'll still follow you no matter what and I can't find a procedure or an AI block that allows them to stand still. I have a sitting model for the mob ready to go, but am unsure on how to implement it. I have GeckoAPI which allows me to put the animation in, but I'm unsure how to make the animation stop and have the mob return to it's original state when right clicked a second time. I'm afraid it might just replace the tamed mob with another untamed one, or just won't do anything at all. Any tips and help with this is also appreciated. 

-Is there a way to make a mob fly?-

I would like my owl to fly like a parrot, but then land every so often as a parrot does too. I can't seem to figure out how to do this either as the parrot isn't an AI type. I'm sure I can figure out the animation bit though, as I have GeckoAPI

-Altering vanilla crafting recipies-

There is an option in which you are able to alter vanilla crafting recipies, however whenever I type in the registry name "arrow" to alter the arrows recipe, it never actually comes through in the game. To be more specific, I have an owl that drops an owl feather, and i would like to use the owl feather to craft arrows as well as use normal feathers to craft arrows. basically, both recipies are available to craft arrows, but this doens't seem to work. How would I go about making the crafting recipe use both feathers as options for the recipes?

I think this is all for now, I hope i can get some answers! But I honestly won't be too upset if all of this stuff is impossible to do in Mcreator right now, since I can live without it. I just think it will really enhance the quality of my mod if I can include them. Thanks for reading!