For breeding Budgies, you need to provide proper space and care. That means a proper breeding box, you can get it in the pet store or even make your own with recommended size for the nest box. I made a lot of articles about breedings, you need to learn everything about breeding budgies before even think about doing it.
Agree, if they are older you need to separate them, they are already old enough. If not, you will need to take care of them, hand feeding and keeping them warm.
I just made an article about getting your Budgie to eat fruits and vegetables. And you can tame your Budgie by doing so. Learn here
You need an area that is closed or shielded from the cold wind and have a heater inside.
Yes, you can. All you need is to provide enough space for both of them. I made an article about Cockatiel and Budgie in the same cage here.
Yes, you can still tame your Budgie, all you need is patience and be gentle and calm to your Budgie. I made a video compilation on how to tame your Budgie, you can watch it here. Quick tip: Hand Feed your Budgie, give him favorite food, apple or spinach.
