motor undervoltage and effect on current and torque

I'm having trouble reconciling a couple different situations:

1) Huge induction motors use reduced voltage autotransformer starting, resulting in lower current and lower torque. Does this essentially result in a new motor speed/torque curve (new LRA torque, new pull up torque, new breakdown torque)?

2) Are multi-horsepower (multi-tap) single phase motors - common for small evaporators - doing the same thing with their speed taps as in #1? The current and torque both decrease.

3) We know that when induction motors receive undervoltage conditions, the current increases. What's the difference between this and #1 and #2?

Thanks,

IJR