Question

find the derivative of f(x)=7 by the limit process

Answer 1

$f'(x)=\displaystyle\lim_{h\to0}\frac{f(x+h)-f(x)}h$

If $f(x)=7$, then

$f'(x)=\displaystyle\lim_{h\to0}\frac{7-7}h=0$

which is what you expect from a constant function.