1. Hinged type expansion joint is modeled as zero length expansion joint. You need not have to model expansion joint as shown on drawing. Axial, transverse and torsional stiffness are considered as rigid. Only bending stiffness is mentioned which is bending stiffness of hinge. Refer CAESAR Applications Guide for expansion joint modeling.

2. Stiffness values: You can put if you have one. Friction values: Yes.

3. Assuming stiffness values at supports will alter your results (compared to results without mentioning stiffness values). Support stiffness values are usually kept blank because they are assumed as rigid in mathematical model. Being rigid it yields conservative results (high loads and stress). However, in real life it is not so. But calculating support stiffness values is a complex activity. You can contact civil/structural department for stiffness values (of supporting structure) if absolutely required.