My First Question is : What are the differences between web Designer and web Developer?

Web designers are for frontend developers who doesnt understand the server side or backend structure. Unless you are web developer who understands both principles.

A web designer is a graphic artist who develops and styles objects for the Internet, typically have a creative mind set,they are able to tap into their creative energy and design the overall layout. while a web developer is one that develops applications and functionality for the Internet. usually think methodically and logically. 

Web designer make design of the web using tools like Photoshop (theme, colors, layers, alignments ... )

Web developer change this design to webpage using codes (HTML - CSS - Javascript ...)

A web designer develops the overall layout and look for websites.

A web developer develops applications and functionality for the websites.