Background
Sometimes F2 can't recover the firmware directly and simply, and the device is stuck in repeated reboots, at this time you need to use DFU mode to fix the device in writable firmware mode.
How-To
Here is a tutorial demonstrating the use of DFU mode to recover the F2, the tools used include the F2 Online Recovery Tool ( https://tool.screek.io/factory_tool/f2/ ), for opening the casing you may need the help of a spoon or something sharper, a small 1 screwdriver will also work if you have one.
A more specialised metal pry bar would also be very handy for opening the casing.