Question

PLEEESE HELLLLLLP If you have a test average of 92 and a standard deviation of 1.8, you generally do well on tests.

Answer 1

Yes, that's true PROVIDED your test scores are normally distributed.

If they are, then more than 99% of your test scores are within three
standard deviations of the mean. 

You told us that 3-sigma = 5.4 .  So less than one score out of every
hundred tests you take is lower than  86.6  or higher than  97.4 . 

You are remarkably consistent, so I guess Jupiter must have been
in its ascendancy next door to the house of Andromeda about an
hour before you were born, or some such nonsense.