Short answer: NO

Generally, by just looking at the graph, it is hard to say if it is a semiconductor to metal to semiconductor transition. To say metallic, the conductivity needs to be very high. In your case it is comparitively very low. Several charge transport mechanism might cross over, which could be leading to such scenarios. Better explanation could be due to change in phases of the material rather than semiconductor to metal transition itself. I redcommend to measure XRD or to carryout something similar experiments to measure the phases of the material as a function of temperature.

Yes definitely

What you have shown in the graph is an example of conductivity in a lightly doped semiconductor. At low temperature, the conductivity is dominated by the activated dopants, whereas at high temperature, there is an additional conductivity arising from the intrinsic conductivity of the semiconductor. As you move from high temperature to low, the carriers, which get ionized from the valence band of the semiconductor to the CB, no longer have enough energy to do so. This is called the freeze-out regime. Normally, the conductivity is constant in this regime. But it can reduce because of the reduction in carrier mobility with the temperature.

It would be better if you could do a four-probe DC resistivity measurement with more data points and Hall effect measurements at different temperatures so that you can quantify the activation energies, carrier concentrations, and mobilities with better accuracy.

Please check out the following discussions as well.

https://warwick.ac.uk/fac/sci/physics/current/postgraduate/regs/mpagswarwick/ex5/techniques/electronic/hall-effect/temperature/

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