<R1> states that a team can only use one robot in VRC. If a team had built multiple robots before the rule was updated, then will it still apply to the team? Would the team be forced to use their first robot?
I believe you are referring to the following Q&A:
Which states: "Once a Robot (defined as Subsystems 1 and 2) is entered in an event under a given team ID#, the Robot may not compete under any other team ID# at any subsequent event.
The intent here is not to prevent teams from upgrading or changing their own robots. The intent is to prevent one Robot being used to compete for multiple teams."
Teams are allowed to change their Robot throughout the season. So if you built one Robot for your first event, and then a new Robot for your second event, this would be legal. You would be allowed to enter either Robot at subsequent events. However, neither of those Robots would be allowed to be entered another a different team number.