Questions about FM Mic Kit Schematic
You are correct
You are correct although it might be a tad lower because of a little bit of base current but the important point is that the BJT will be biased.
No this isn't important - the output impedance of the microphone circuit will be approximately 27K (R1 acts as drain resistor for the internal JFET in the mike)
C1 doesn't need to be polarized - I would pick a ceramic capacitor and avoid an electrolytic because it's unclear which side will have the more-positive voltage
C2 and C3 hardly do anything at audio frequencies but, at 100MHz they ensure that the base is strongly de-coupled - this improves the modulation process and may in fact prevent it if they were not there.
C4 injects the positive feedback power into the emitter and the collector will naturally be in phase and produce a higher AC voltage thus ensuring oscillation. There's a lot more to how this works and how the centre frequency of the tank will be slightly shifted from theoretical but this appears too much to discuss at this point.