Reuse/distribution of signals
What you call "reuse" of signals is usually called fanout. Fanout refers to the number of circuit inputs that can be connected together and driven by a single circuit output. The maximum number of inputs that can be driven by a given output depends on many factors, including


current provided by output vs. current required by inputs
capacitance of inputs vs. required rise and fall times
length of signal lines vs. acceptable noise level


If necessary, buffers can be added to drive higher numbers of inputs.

Bidirectional signal lines are often switched in direction. The data lines in a USB cable are bidirectional, for example. The usual requirement is to design the entire circuit so that only one device is driving a particular signal line at any given instant in time.