Having issues building & running a Sitefinity project

I am having issues trying to build and run an already built Sitefinity Project. We have received a Sitefinity project from a client. This project was being developed by someone else earlier, now the client is deciding to give this project to us.

 When I tried to open the project using Visual Studio, The Framework was set to .Net 4, When I built the project I got some compile time errors like : "The type or namespace sitefinity.modules does not exist in the namespace ...". When I switched the Framework to 4.5 the project built successfully but with various warnings of dependent assembly conflicts like these :

"No way to resolve conflict between "System.Net, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" and "System.Net, Version=2.0.5.0, Culture=neutral, PublicKeyToken=xxxx, Retargetable=Yes". Choosing "System.Net, Version=5.0.5.0, Culture=neutral, PublicKeyToken=xxxxx" arbitrarily.
1>  No way to resolve conflict between "Telerik.Windows.Documents.Flow, Version=xxxx, Culture=neutral, PublicKeyToken=xxxx" and "Telerik.Windows.Documents.Flow, Version=2015.1.225.40, Culture=neutral, PublicKeyToken=xxxxx". Choosing "Telerik.Windows.Documents.Flow, Version=2015.2.713.40, Culture=neutral, PublicKeyToken=xxxxx" arbitrarily.
1>  Consider app.config remapping of assembly "Telerik.Windows.Documents.Flow" etc

 Though the project built without any errors, But when I opened default.aspx page of the website I get some other error with stack trace which are described below:

The previous developer may have deployed the project on Azure because the web.config contains commented sections of Azure settings, I have not. I just deployed it on Local IIS 7+ with DB on MSSqlServer2012(local). When I try to build and run the site I see the error: "Unable to cast object of type 'System.String' to type 'System.Type' sitefinity" . The web.config snippets  mentioned in this thread: "www.sitefinity.com/.../getting-exception-when-running-sitefinity-application-in-azure-cloud-services were commented out already. And because I have not deployed it on Azure, I think they should remain that way. What to do in this case? I don't know whether the settings should be fetched from file system or DB. I only have a DB and a Sitefinity Project which the client provided. The web.config contains commented sections of windows azure. When I run the application I get the same error as : "Unable to cast object of type 'System.String' to type 'System.Type' ..." .

What is the solution here. In my scenario I just want to run the application, We don't have direct access to the previous developer. How can I make my application run considering my constraints. I dont have access to the Sitefinity Project Manager right now. Once we are in a position to run the application, then we will ask the client to provide us other resources. If we think that it is not in our scope right now to do this in minimum time we will not take this project. Kindly help me in this regard. If the project runs, we may be able to acquire this project from the currently assigned developers.