Non-linear amplification circuit
The Diode's Anode is the same node as the Inverting Input. The Voltage Divider at it's Cathode is 10*200/(200+800)=2-Volts. So the Maximum Inverting Input Voltage is 2.7V. Since the Feedback voltage divider provides 1/3 of the output to the Inverting input the Max Vout will be 2.7*3=8.1 as any Vout exceeding that will forward bias the Diode. So Your Non-Inverting input is actually limited to a 2.7-Volt Input as well (which will output Vout = 8.1-Volts. I don't know how you fit that in an algebra equation. But uhhh that should help, It answers #2.

edit: your title says "Non-Linear", so their is likely some "non-linearities" in there. Because of the Diode

Good Luck!