Two Round Feistel network
I read that two-round Feistel network is not a secure PRP

That's easily seen:
                                            
It holds $P_L\oplus C_L=F_0(P_R)$. That implies a distinguishable property: for any fixed $P_R$ and whatever the round function $F_0$, when we flip bit(s) in $P_L$, that flips the corresponding bit(s) in $C_L$ and leaves the other bit(s) in $C_L$ unchanged.
That property allows a break under Chosen Plaintext Attack.