Explanation on why there is no feedback in the circuit for higher voltages of input signal
Consider just the current source I1 and the four diodes around it. With no other current imposed on it, all four diodes are conducting, with half of I1's current flowing around each of the side loops.

Any current applied in the horizontal direction must flow through D2+D5 or D3+D4, depending on its sign. This current will add/subtract from the current supplied by I1 as appropriate, reducing the current in some diodes while increasing the current in the others.

Now, what happens if that external current tries to rise above 1 mA? Two of the diodes will cut off altogether, and the external current can ONLY flow through I1, steered by the remaining diodes. This means that the current CANNOT rise above 1 mA, and that the effective impedance of this circuit becomes infinite, effectively breaking the feedback loop.