A downgrade path is not supported convert version 782 to 706 and earlier

I am creating one application where I have used ASP.NET MVC with Entity Framework 4.5.2 and trying to access the SQL Server but it gives me an error that I can't access any database so I just convert it to the single user mode.

Now after converting it to Single User mode the new error comes when I am trying to access in Server Explorer, Data Connections (Default Connection), it shows me the below dialog. I am not understand what is going wrong.

I have SQL Server version 11.0.2100.60.

Please some one help me to solve this issue!

Ufffff after so many solutions applied I found one from it.

Steps:

1) Change Instance name in Visual Studio Link:

Under Tools > Options > Database Tools > Data Connections > SQL Server Instance Name. set (LocalDB)\MSSQLLocalDB

2) Change your connection string:

From:

<add name="DefaultConnection" connectionString="Data Source=./SQLExpress;AttachDbFilename=|DataDirectory|\DBName.Service-20160924032113.mdf;Initial Catalog=DBName.Service-20160924032113;Integrated Security=True;"providerName="System.Data.SqlClient" />

To:

<add name="DefaultConnection" connectionString="Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\DBName.Service-20160924032113.mdf;Initial Catalog=DBName.Service-20160924032113;Integrated Security=True;"providerName="System.Data.SqlClient" />

3) Remove User Instance=True from Connection String.

Thanks to James P and Mark Homer for excellent response.