Why does the resistance of metallic conductors and semiconductors change differently with a change in temperature?

$A$ cylindrical resistor is connected to a battery with emf $5 \ V$. The resistance per unit length varies as $\rho(x) = \rho_0 \left(\frac{x}{L}\right)^\alpha$,where $\rho_0$ and $\alpha$ are constants and $x$ is the distance from one end of the resistor. The product $\rho_0 L$ is $10 \ \Omega$,where $L$ is the length of the resistor. If the thermal power generated by the resistor is $20 \ W$,then the value of $\alpha$ is:

If a copper wire is stretched to make its radius decrease by $0.1\%$,then the percentage increase in resistance is approximately .......... $\%$

Why does the resistivity of a metal increase with an increase in temperature,or why does its conductivity decrease with an increase in temperature?

What is the resistance between the rectangular faces of a block with resistivity $3 \times 10^{-7} \, \Omega \cdot m$ and dimensions $1 \, cm \times 1 \, cm \times 100 \, cm$?

The resistance ${R_t}$ of a conductor varies with temperature $t$ as shown in the figure. If the variation is represented by ${R_t} = {R_0}[1 + \alpha t + \beta {t^2}]$,then