Answer:
- On the vertical axis we find the percentage identity between the model
and template sequences. The horizontal axis indicates how long the
bits are in those two sequences that actually could get aligned. Above
the curve, you find alignments that are good enough to allow for homology
modelling. Below the curve we just don't know.
- False. Below the curve we don't know. We don't have good tools to tell
us if the sequences are homologous or that they accidentally look a bit
like each other. But if you have other knowledge that tells you that
modelling should be allowed, then go ahead, build your model. But be careful
not to trust the model too much...
- It isn't in the plot, but at 52% height far to the right of the plotted part
of the curve.