1). The probes connect the metal and semiconductors so that we can allow current flow as germanium could not produce current. The probe provides physical contact with germanium.
2). It is necessary to adjust the probes in collinear. I do not understand what you mean face to face? This is because
a). To allow a small amount of currents (large currents are not good for measurements)
b). Uniform potential gradient.
3). In reality the measurement of Resistance itself is a concept that means less. We can only measure resistivity because it is associated with physical parameters such as length and area. This applies to all materials. The resistance is property of the material, so it changes with physical dimensions. While resistivity is the amount that remains constant for a given material.
4). No. That does not give you the correct value of resistivity. This is because the current does not go uniformly through germanium (as opposed to metals)
5). If you switch them, the milli- voltmeter does not give you any reading at all. As you are aware that the current always chooses the shortest path, so the current is confined to the small portion. There for physically no current will flow through external probes. Therefore, your voltmeter does not display any reading.
6). There is a known formula for this. That takes exponential form. In this way, the electrons need less energy to reach the conduction band (they obtain the energy of the temperature), reason why the resistiance decreases exponentially and therefore the semiconductor now becomes a good conductor. Therefore the voltage falls as V = i * R so that R drops V falls at constant current i.
Thus, at high temperature, semiconductors show an ohmic relationship (something like v = ir) but not at high extreme temperatures.