it's best to put them inside the van towards the rear. this should be done while the van is not moving. like in your driveway or a parking lot. hope this helps.
No. No US cargo vans come in a three seat configuration. Some are available as an 8 or more passenger vehicle. None offer three seats, nor do any offer a front bench seat. Sorry.
No, I'm afraid not. It's for the safety of the person. If the vehicle got into an accident, the person in the back would almost definitely die. Also, if you get pulled over and the person in the back...