I am by no means a vehicle expert but here are some thoughts.

Docent it say the forced movement is at the beginning or end of your turn. So if your travel at speed 2 and are at close range you could do the reposition maneuver to be engaged ?

So say your chasing the bad guys in a car both travelling at speed 2 down the golden gate bridge. Your in car A. Car A is short distance away from car B at the end of A turn driver spends 2 strain and takes the reposition maneuver to be at engaged range.
Or if they start at short he starts with reposition.

If at 0 speed it makes sense not to reposition unless your like hovering or something dont know I guess you would have to fire up the engines and then reposition.

I was just re-reading the vehicle rules for an upcoming campaign. Let me see if I can help out with some of these questions, though by no means am I an expert in the vehicle rules of Genesys.

Q1. If a vehicle has non-zero speed, it is moving its forced movement. And reposition is the only maneuver/action that grants range band movement. So the answer would be yes.

Q2. I don't think so. There is no maneuver to "move" per se, other than reposition. A vehicle's movement is the forced movement based on their speed which happens either at the beginning or end of their turn. You totally can fly to one range band away: say a vehicle is flying at 1 speed that's 2 range bands of forced movement. If the pilot is at short range, and attempting to move to medium range, then they can move from short to medium back to short, then reposition to medium. Effectively spending one maneuver to move one range band.

Q3. No. I see no problem with it being 1+ speed.

Q4. No. I mean you could, or you can just use reposition for essentially the same thing. I was thinking of Star Wars stuff, I was like "Why would you be engaged in melee with vehicles?" Then I thought about mecha settings where that totally would happen. I'd just use reposition for essentially the same maneuver as moving into and out of engaged.

Q5. But that's not true. Vehicles move because they have a non-zero speed. Reposition essentially 'corrects' overshooting your desired destination by one range band.

Personally I really like Genesys's vehicle movement rules a ton more than the Star Wars games. It keeps in mind that vehicles that have greater than zero speed are constantly moving and flying around. Where as at personal scale a human can be standing around in combat, or at least taking very few steps that wouldn't constitute a full maneuver, like footwork in fighting. You're not moving trying to gain distance, rather you're simply stepping around to shift your weight. A vehicle doesn't have that kind of stationary position, unless it's actually stopped relative to the other things around it.

Honestly, if you were so inclined, I doubt it would be a huge deal to change the reposition maneuver from "1+ speed" to "any speed". I can and have totally seen Star Trek ships blast a thruster to move over a little bit but otherwise start and end at zero speed. Which would be difficult to show off in the Genesys system as it sits. Also it would make sense for like a mecha settings where two mechas are sword fighting in space engaged, which should probably be at zero speed, but as long as they were going the same speed it wouldn't matter, then one wants to disengage. But also in the same scenario the mecha could just do an accelerate maneuver and move two range bands for essentially the same effect, except they'd be two range bands apart.

The problem is that Engaged really isn’t a range band, it’s more a condition imposed on the attacker and target. My suggestion was a modification of the Reposition Maneuver to this:

Reposition
Pilot Only: Yes
Silhouette: Any
Current Speed: Any
The pilot may move the vehicle up to one range band, move within short range, or to engage or disengage a target. This maneuver reflects minor repositioning to avoid obstacles, close or widen distance in a chase, or otherwise shift within the environment in small ways.

This addresses all the problems and makes it easier to address things like boarding actions, docking, and Mech Combat.

Standard and Vehicle Combat becomes easier to get your head around when you understand Engaged is a condition not a range band.

Engaged didn’t even exist in Star Wars vehicle combat, it would seem that the developers got stuck thinking of two separate systems and had ideas that didn’t quite get fully explained in the rules.

your rewording of Reposition definitely makes the most sense, I wouldn’t be surprised if that’s what they had originally intended

Close range however did exist. They just replaced it with Engaged so the language was the same.