Exactly which 'clock frequency' are you referring to? There are a number of data sheet parameters that refer to min/max clock frequencies.
For example, 'clock tree' performance range maximum is anywhere from 350MHz to 500MHz, depending on speed grade of the device.
You have to ask a lot more specific questions.
Hi, I would like to clarify if you are looking for the PLL input clock frequency of Cyclone IV devices. You can refer to the Cyclone IV device datasheet, Table 1.25: