It depends on the specific vehicle's gear ratios. Let's say the
car has a closed-ratio "box", skipping from 4-2 may not have as
drastic effect in engine braking as another car with a long-ratioed
one.. The rpms will thus not shoot up as much. Skipping gears while
down-shifting may cause the engine to over-rev and the vehicle to
skid if the speed is too fast, as too much power is channelled to
the wheels. Ultimately, the drivetrain will be damaged.
As for starting off in 2nd gear, it all depends on the car's
torque, and of course, gear ratio. Generally, diesel-powered
vehicles have good low-end torque to allow starting from 2nd, while
for some small-engined petrol-powered cars, doing so will may
simply cause it to stall..
