A1) You don't need a slave connected for the master to exercise the I2C outputs
A2) Did you check that the address range you defined in the interconnect is the same as it is expected by your .c example code?
A3) You don't need additional HW (Verilog or other) code for this to work. I guess the cause of the problem can be on the address range.
As a proposition for you to debug, try to make a simpler task to check that your system is alive. For example, blink some LEDs from your PS processor using Vitis. Once you have succeeded doing that, go back to more complex problems.
As an additional point, you need to learn how to debug. How to debug the SW using the VITIS, and how to debug HW usign testbenches and ILA (Integrated Logic Analyzer). If you can't see where your problem is, it is difficult to solve it.
