What is the difference between a mistake and an error in the context of physical measurements?

If the length of a cylinder is $l = (4.00 \pm 0.01) \; cm$,radius $r = (0.250 \pm 0.001) \; cm$,and mass $m = 6.25 \pm 0.01 \; g$,calculate the percentage error in the determination of density.

$A$ scientist performs an experiment in order to measure a certain physical quantity and takes $100$ observations. He repeats the same experiment and takes $400$ observations. By doing so,

Using the expression $2 d \sin \theta = \lambda$,one calculates the values of $d$ by measuring the corresponding angles $\theta$ in the range $0^{\circ}$ to $90^{\circ}$. The wavelength $\lambda$ is exactly known and the error in $\theta$ is constant for all values of $\theta$. As $\theta$ increases from $0^{\circ}$:

In an experiment,four quantities $p, q, r$,and $s$ are measured with percentage errors of $3 \%, 2 \%, 3 \%$,and $1 \%$ respectively. Quantity $A$ is calculated as follows: $A = \frac{pq^2}{r^2 s^4}$. The percentage error in $A$ is: (in $\%$)

$A$ force $F$ is applied on a square plate of length $L$. If the percentage error in the determination of $L$ is $3 \%$ and in $F$ is $4 \%$, then the permissible error in the calculation of pressure is (in $\%$)