SharePoint 2010 creates a new instance for SharePoint server.

I have installed SP 2010.My env is Windows server 2008 R2 and SQL 2008 r2 (10.50.1600). When I install the SP 2010,
 
configuration wizard (Start the SharePoint Products Configuration Wizard) directly goes to configuration wizard and installed SP 2010 server successfully.

It skips the below Manual configuration.
1. Specify Configuration DB settings
2. Specify Farm Security settings.
3. Configure CA Web Application settings. etc...

So I get the new SQL instance with the name <MachineName>\sharepoint.
This new Instance is looking SQL 2008 version(10.0.2531).

Now I face the below issues,

1. When I restore DB backup, i get the compatability issue 
2. Unable to restore the SP2010 site which is backuped from SQL 2008 r2 (10.50.1600) has 9GB size.
3. Unable to extend the DB size from 4096 MB. 
How to avoid create new SQL instance with the name <MachineName>\sharepoint and install in SQL server default <MachineName> instance?

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Loganathan S