Robert, a professional hacker, is attempting to execute a fault injection attack on a target IoT device. In this process, he injects faults into the power supply that can be used for remote execution,

Frequency/voltage tampering generally refers to sustained or controlled alterations, whereas 'glitching' specifically describes transient, short-duration manipulations intended to induce faults, which is what Robert is doing to skip instructions.

Optical fault injection uses light (e.g., lasers), and electromagnetic fault injection (EMFI) uses electromagnetic fields to induce faults, neither of which is described as Robert's method of manipulating the power supply or clock network.

A temperature attack involves altering the device's operating temperature to exploit temperature-dependent behaviors or induce faults, which is not the method Robert used.

Power glitching involves manipulating the power supply voltage to induce transient faults, which can lead to instruction skipping or privilege escalation. Clock glitching involves manipulating the clock signal to disrupt the device's synchronous operations, also causing instruction skipping or unexpected execution flows. Robert's actions of injecting faults into the power supply and clock network precisely match these techniques.