— Function: variable-customized-p symbol

Returns true if symbol has been customized by the user, false otherwise.

— Function: variable-declared-p symbol
— Function: variable-default-value symbol

The variable-declared-p function returns true if the variable named symbol has a default value declared for it, false otherwise. The variable-default-value function returns the default value of that variable, or nil if no such default value exists.

— Function: variable-type symbol

Returns the customizable type of the variable named symbol.