please provide the full actual circuit using gates and not block notation, thanks

you can draw by hand or online either way works

Adder/Subtractor Using four of your full adder components (described above), in a separate circuit (called ADD_SUB) create a 4-bit adder/subtractor component. The circuit will take two sets of 4-bit inputs (A3-AO and B3-BO), plus two additional inputs SUB (if true, SUBTRACT, otherwise ADD) and ENABLE (if true, all outputs are enabled using tri-state buffers, if false, all outputs are disabled). The circuit will produce a 4-bit sum (S3-SO) or difference (when subtracting). The basic circuit is given below (without the ENABLE input). In this circuit, the Kinput is the same as our SUB input