The maximum clock frequency for the 74HC165DB,118 is 25 MHz, but it can vary depending on the operating voltage and temperature.
Yes, the 74HC165DB,118 can be used as a level shifter, but it's not recommended as it's not designed for that purpose. It's primarily a parallel-in/serial-out shift register.
The asynchronous reset (SRCLR) input should be tied to VCC through a pull-up resistor or connected to a logic high signal to prevent accidental resets. A low signal on SRCLR will reset the shift register.
The recommended operating voltage range for the 74HC165DB,118 is 2.0 V to 6.0 V, but it can operate down to 1.5 V with reduced performance.
Yes, the 74HC165DB,118 is compatible with 5V systems, but ensure that the input signals are within the recommended voltage range and that the output is not driven beyond the maximum current rating.