Atendency to apply a rule of grammar at all times is a type of . idiom, overgeneralization,
dialect, colloquialism

A tendency to apply a rule of grammar at all times is a type of overgeneralization   T

he rest of the choices’ definitions are the following:
An idiom by dictionary definition is an ‘expression that cannot be understood from the meanings of its separate words but that has separate meaning of its own’.  
A dialect by dictionary definition is a word spoken in a certain area or group of people with its own set of language structures – grammar, words, pronunciations, etc.  
Colloquialism are informal words used by people in a certain area whom they alone could understand.