The maximum clock frequency for the SN74HC595DBR is 25 MHz, but it can vary depending on the operating voltage and temperature.
To ensure that the output pins are in a known state during power-up, you can use the output enable (OE) pin to disable the outputs during power-up, and then enable them once the device is fully powered up.
The MR (Master Reset) pin is used to asynchronously reset the shift register and output latch, clearing all outputs to a low state.
Yes, the SN74HC595DBR can be used as a level shifter, but it's not recommended as it's not designed for that purpose. The device is primarily intended for serial-to-parallel data conversion.
The latency between the clock signal and the output data is due to the internal clock-to-output delay. You can account for this delay by adding a clock cycle or two to your design to ensure that the output data is stable before sampling it.