These questions are a tell tale sign of ignorance. Lets apply logic to the questions.
I exist. Things around me exist and are tangible. God is not tangible mentally or physically. So, in order to make god tangible I need faith. Faith is the direct opposite of tangibility.
Tangibility vs Faith = God vs Logic
As for the second question. If you did some research you would see there is plenty of overlap between religions. The differences could come from a multitude of reasons but an easy one is cultural development over time.