Can error be completely eliminated?

In an experiment,four quantities $a, b, c, d$ are measured with percentage errors $2\%$,$1\%$,$3\%$ and $5\%$,respectively. Quantity $P$ is calculated as $P = \frac{a^2 b^2}{c d}$. Find the percentage error in measuring $P$. (in $\%$)

$A$ current-carrying conductor obeys Ohm's law $(V = RI)$. If the current passing through the conductor is $I = (5 \pm 0.2) \text{ A}$ and the voltage developed is $V = (60 \pm 6) \text{ V}$, then find the percentage error in resistance $R$.

Error in the measurement of radius of a sphere is $0.2\%$. The error in the calculated value of its volume is ......... $\%$

Out of absolute error,relative error,and fractional error,which has a unit and which has no unit?

Two students $P$ and $Q$ perform an experiment to verify Ohm's law for a conductor with resistance $R$. They use a current source and a voltmeter with least counts of $0.1 \, mA$ and $0.1 \, mV$,respectively. The plots of the variation of voltage drop $V$ across $R$ with current $I$ for both are shown below. Which statement is most likely to be correct?