1.
You'd have seen more of the island if you'd hired a car, if you'd hired a car, you'd have seen more of the island if you'd hired a car.
2.
If I'd known they were coming I'd have got more food in, I'd have got more food in, if I'd known they were coming I'd have got more food in.
3.
They wouldn't have spent the day traveling if they'd got a flight, if they'd got a flight, they wouldn't have spent the day traveling if they'd got a flight.
4.
If she hadn't heard it for herself she wouldn't have believed it, she wouldn't have believed it, if she hadn't heard it for herself she wouldn't have believed it.
5.
We'd have found another hotel if we hadn't paid for the room already, if we hadn't paid for the room already, we'd have found another hotel if we hadn't paid for the room already.
6.
If he traveled alone he'd have met more people, he'd have met more people, if he traveled alone he'd have met more people.