The seat will fold down to about a 30-degree angle (not completely flat, but very comfortable for a sleeping child).

You could probably fit one into one of the seats, but it doesn't have any safety latch attachments, so if it were to tip there might be a risk of injury.

the weight limit is 50 lbs per kid or 100 lbs together.

I bought this same stroller in red and it only came with one swivel wheel. It may mean that the rear wheels are 12" and the swivel is 16". Or vise versa. I know that the swivel wheel and the rear wheels are different sizes. Not sure which is bigger but that maybe what it means.

The seats are not detachable from one another, but you can still use it with just one child.

No, there is no handbrake. From my experience though, I have never used the handbrake on my past joggers. I just use the strap around my wrist

it comes off, but you can tell something is supposed to be there....but it does come off pretty easy, and you can just leave it off....it's not so close to the seats that it makes it uncomfortable for the kids, though.

Yes it does and it is functional.

Each model has its own model number. The main difference between the Safari models is color.

Yes. You can have one child fully reclined and the other one sitting.