Question: I know this is not a technical related question.But i do not have any idea.I am going to develop a project which should be supported in both phone and tablet.Is it possible having one project working for both tablet and phone ?

Answer: 
MySql can handle very large projects, it's stable, updated and free, so I think you shouldn't think to go on with Access.  

Connecting to MySql will be quite easy: include MySql.Data.dll and change db connection string, it's easy and you'll find a lot of examples on internet.  

If your app should only talk with db in intranet, simply install MySql on a server and connect your app using server ip and port.
the number of users for your app shouldnt matter, u should use mysql simply because it's free. robust, can handle heavy traffic and very professional. it has pretty much clients for any programming language and there are tons of documentation in the internet.

i hope this will help