Which of the functions defined below are NOT one-one function(s) ?

The function $f\left(x\right)$ defined on the real numbers has the property that $f\left(f\left(x\right)\right)·\left(1+f\left(x\right)\right)=-f\left(x\right)$ for all $x$ in the domain of $f$. If the number $3$ is in the domain and range of $f$, then the value of $f\left(3\right)$ is

Solve the following problems from functional equation:

Suppose $f$ is a real function satisfying $f\left(x+f\left(x\right)\right)=4f\left(x\right)$ and $f\left(1\right)=4$, then the value of $f\left(21\right)$, is