Here is a great website for you to look over. It will likely answer all of your questions, and even answer questions you didn't even think of yet. It is developed/managed by one of the moderators of this forum.
The question about aggression may be difficult to answer. Both our female veiled chams are veritable witches. They hide, hiss, run, try to bite, etc. During all seasons of the year, and without regard to hormonal changes. We disturb them as little as possible. When the one girl was gravid we blocked her enclosure from view, so she could not even see us in the room.
I don't know that veiled breeding is ever seasonal. It does not appear to be in our household.
Yes, veiled chameleons can lay eggs even if they've never been bred.