Do airlines not have the option to request their thrust settings - ie either for performance, relaibility or efficiency.
Not quite sure what you're getting at here.
What is the idea behind the derated options? Are they for weather/runway conditions?
I think you might be referring to FLEXIBLE take off thrust. This is an approved method for reducing Take Off power to save wear and tear on engines.
Derating is slightly more complex and has to do with an engineered permaneant reduction in the available thrust of the engine in all conditions, and the pilot has no control over this reduction.
Sometimes that term DERATE gets misused and confused with the terms "Flexible T/O Thrust" or "Reduced T/O Thrust".
Is there not the possibility that Take-off could be different to Go-Around. Although they are the same, I think there is the possibility for them to be different.
Again I think you are referring to the FLEX T/O option. In that scenario, yes, there is indeed a difference between the T/O power which you are using and the full T/O power actually available.
But if you need to obtain full power all you have to do is push the thrust levers forward into the TOGA detent on the throttle quadrant.
Does this answer your question?