I have SN74HC4040 12 bit counter, however, I need only 10 bits and then reset it back to 0. Would it be reliable to use 11th bit as an input to the CLR (reset pin)? Basically, when the counter transitions from 1023 to 1024, the 11th bit becomes high, which, in turn, sets CLR to high and resets the counter. It seems to work, but I do not know how to check the counter's state during the reset period.
You don't need to do any of that. Simply ignore the upper 2 bits. Now you have a 10 bit counter that automatically wraps around from 1023 to 0.