Haven't seen these specific questions before (not an instructor but done all ATPLs). If they are feedback, they may not be accurate questions so beware but anyway, here's my stab...
Q1) Flying at a constant mach no.what is true of Thrust and fuel flow??
A) Decrease in proportion to ambient Pressure with constant temp
B)Increase in proportion to ambient pressure with constant temp
Flying at constant mach (mach 1 is a function of temperature ONLY). With higher pressure for a given mach number, this means the air will be relatively denser and therefore offer greater thrust and fuel flow so I would go with B. On the other hand I'm arguing with myself that the air being denser means that the engine doesn't need to spin so fast to generate the same thrust to travel at the constant mach no.
Q2) When is the greatest IAS achieved in a piston A/C?
A) At the lowest altitude
B) At the optimum cruise alt
C) At the service ceililing
D) At the Absolute ceiling
Really not too sure about this one. Question doesn't seem right. We generally fly at a constant IAS (CAS) in piston aircraft but the TAS will increase with altitude due to the reduction in density.
The highest IAS is VNE for a piston.
Q3) For an aircraft flying at the LRC speed what happens to specific range and fuel to time ratio.
LRC is a speed that is faster than the best range speed but only uses a relatively small amount of extra fuel. (i.e. get there significantly quicker without too big a fuel penalty). If that allows the aircraft to fly more hours a day (higher utilisation) it may actually be a cost saving. Specific range (if I remember right) is tied to specific fuel consumption which is KG of fuel burn per KG of thrust per unit time. SFC will increase at LRC when compared to best range speed. I'm not sure about the fuel time ratio (don't remember it) but it sounds like the same thing??
I only answered because you posted it as a last minute need - hope my thinking is on the right lines but you'd be better checking with a Performance ground instructor such as Alex at BGS or Peter at GTS Bournemouth.
Good luck.