If $f:\{1,2,3,4\}\to\{1,2,3,4\}$ is a function such that $|f(\alpha)-\alpha|\leq 1$ for $\alpha\in\{1,2,3,4\}$, then total number of such functions is
Number of correct statements: I) $f,g:\mathbb{R}\to\mathbb{R}$ with $f(x)=x$ if rational, $0$ if irrational and $g(x)=0$ if rational, $x$ if irrational. Then $f-g$ is one-one and onto. II) $f(x)=\sin x+\cos ax$ is periodic only if $a$ is rational. III) If $f:A\to B$ and $g:B\to C$, $g\circ f:A\to C$ is one-one, then $f$ must be one-one.