Each of the GPIO pins can be configured by software as output (push-pull or open-drain, with or without pull-up or pull-down), as input (floating, with or without pull-up or pull-down) or as peripheral alternate function. But you can change this configuration dynamically. I would suggest to go in our st community https://community.st.com/ to get further support FYI : If you set it as output the pins is still working as input.
