Pedalz -
I'm not the best person to reply to your ramp query - he'll be along later! - and it's been largely answered already, but the bare bones are this;
Ramp 1&2 Green system, back up of yellow, 3&4 Blue, backup yellow.
Any continuous surge at supersonic speed would affect the adjacent engine, hence the requirement to close all 4 throttles.
Cheers,
EXWOK