How to choose which function to use depending on the parameter value? (MUX and Gates implementation)
I'd do A3A2A1A0 as minterms AND maxterms.  See which gives minimum gates.  The gate count will be close but there is some overlap as maxterms. There is no simplifying 0,5,6,11.  All are unique.  So decode for A is big and messy either way you go.  4 4-input to a 4 input with 2-input gates is messy.  Use this signal to feed MUX as required.
So AB+C and B+C are similar.  Use 4 2to1 MUX to switch between A and 1.  MUX * B + C.  No idea how you are doing the multiplication and addition.
&amp; 4.  Me thinks 1 and 2 sort out 3 &amp; 4.


$$(\overline {A3} + \overline {A2})(\overline {A3} + {A1})........$$