But that is not the absolute truth because different people have different ideas and different qualities and characteristics they assign to their Higher Power.

The quality of something or the characteristic of a Mystical deity or presence cannot be absolute either because quality and characteristics are a description of something, not the thing itself.

That seems to me more like an opinion or a subjective belief to the person who believes that.

Also, their belief in it does not make it a absolute Knowing because believing and knowing are different.

Absolute truth comes from knowing and not believing in the thing in question.