Do players have to switch to their "positions" In a 4-2 VB rotation?
I think sometimes people confuse rules and positions/strategy. Keep in mind the ONLY thing in the rules is that your players must rotate one position each time you win the serve. Other than that, the rules don't mention "switching" or "4-2" or anything like that. So no, you don't have to switch your positions. However, it's usually a good idea to do so, since it's much easier to pass the ball to the center instead of the outside. Ultimately though, just do what works best for your team.
In any system, players on both teams have to be in the proper rotation order at the time of the serve but once the serve is contacted, they can switch positions. In the 4-2 the setter in front row switch to the middle as soon as the serve is contacted, then stay in the middle until the rally is over. For serve receive when your setter is either left front or right front, most teams will do a stack on that side so the middle front is passing behind the attack line and closer to the middle of the court than the setter, and that would put the middle front in position to hit from that side. When the setter rotates to the middle front position, no switch is needed because they are already where the setter would go. Once the second setter rotates to the front row, the same thing happens except with a different setter. The previous answer is wrong to say that passes should be based on where the setter is located - passes go to a position near middle front and it is up to the setter to get to that spot before the pass does, and this is regardless of whether you run a 4-2, 5-1, or 6-2. There is no such thing as a 6-1 offense.
In any rotation, the players ALWAYS have to rotate when it is time (you always rotate clockwise if your team wins the point when the other team is serving). So when you say 'switching' to their spots? in a 4-2, you don't necessarily need to run all over the place like in a 6-1 etc. As there is a setter always in the front row. Just that the team would need to pass the ball appropriately to the setter based on where the setter is located. The setter will usually want to set from almost center. So the setter might need to move to the center after a serve, the downfall of this is you only have two attackers in front and two blockers up front. So this is probably one of the most basic and easy rotations, but it is also one of the weakest. When you play a 5-1, 6-1, 6-2 etc you have 3 hitters and blockers MOST of the time. Back row players can't attack at the net or block at the net. Only from the 10 foot line. They can come up to pass, but that's it.