questions about game play (yes I am new)

Im wondering why when you attack why your unkilled troops dont return to camp? I mean if they survive then why not get them back?

Also why does your gold beforere their production produce anything while upgrading? Same with barracks why cant you train while upgrading?

Plus why cant, after breaking through walls, can you direct where you want your troops to attack? Example: i want my troops to attack the opponents mortar before anything else.

Im just wondering what the creators reasoning behind this is.