How to measure component voltage?
You can only measure the voltage of a device that generates a voltage (such as a battery).

Some devices, like LEDs, have a fixed voltage at which they operate, and for that you can pass a fixed current through it within the specifications and measure the voltage dropped across it.

Similar for other devices - have them working in a circuit and measure the voltage dropped across it - however that isn't the specified voltage, only the voltage it is running at for that specific scenario.

To find out the voltage limit you instead need to consult the datasheet for the device. That will tell you all you need to know.