SD.h change question

Projects General Guidance
1

Can SD.h be made to operate at higher baud rates? If so, is there any hardware limitation for this?

2

Can SD.h be made to operate at higher baud rates?

This question doesn't make sense. Communication between the Arduino and the SD shield is via SPI, not serial.

If so, is there any hardware limitation for this?

Aside from the fact that serial communication is not used? Can't think of any.