The PCF8574 can support I2C bus frequencies up to 400 kHz.
The PCF8574 can be reset by pulling the SCL line low for at least 10 ms.
The PCF8574 can sink or source up to 25 mA per I/O pin.
Yes, the PCF8574 can be used as an input expander by configuring the I/O pins as inputs and reading their states through the I2C bus.
Each PCF8574 device can be assigned a unique address by connecting the A0, A1, and A2 pins to VCC or GND, allowing multiple devices to share the same I2C bus.