Take $f(x)=e^{x^2}$ then $$\frac{f'(x)}{f(x)}= 2x$$ which is not bounded on $\mathbb{R}$
Also if $f(x)$ does not vanish it does not mean that $\frac{1}{f(x)}$ is bounded for example take $e^{-x}$.
Take $f(x)=e^{x^2}$ then $$\frac{f'(x)}{f(x)}= 2x$$ which is not bounded on $\mathbb{R}$
Also if $f(x)$ does not vanish it does not mean that $\frac{1}{f(x)}$ is bounded for example take $e^{-x}$.