Restore bckup from 2012 to 2008,2008R2.

Can I restore database backup taken from 64-bit server to 32-bit server and vice-versa?
Absolutely, You can do it as backups are just a file. Just like any other files (JPG, docs, etc) you can use them in 32 bit and 64 bit application server without any issue. The issue related to the platform should only arise with the application (like SQL Server, Office etc.).

Can I restore a SQL Server 2012 database to earlier versions like 2008 or 2005? Or How to Downgrade my Database to earlier versions?
 No, you can only move forward. This means, you can restore the database from 2005 or 2008 to 2012 version but can not do it in reverse order. The next most popular question  is if we can’t restore a SQL Server 2012 database to earlier version what is the next best option? 
Yes, we can Do it by Exporting the data to particular database on server.

How to bring MSSQL server online.

SQL 2008 R2: HRESULT: 0×80071736 SQL Server could not be brought online

Connect to SQL server (2005, 2008, 2008R2) Instance

Check In to particular server, check for properties.

Select cluster (Domain Instance), give all permission.

1.       Make sure that you know the name of the cluster and the name that the clustered service or application will have.

2.       On a domain controller, click Start, click Administrative Tools, and then click Active Directory Users and Computers. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.

3.       In the console tree, right-click Computers or the default container in which computer accounts are created in your domain. Computers are located in Active Directory Users and Computers/domain node/Computers.

4.       Click New and then click Computer.

5.       Type the name that you will use for the clustered service or application, and then click OK.

6.       On the View menu, make sure that Advanced Features is selected.

When Advanced Features is selected, you can see the Security tab in the properties of accounts (objects) in Active Directory Users and Computers.

7.       Right-click the computer account you just created, and then click Properties.

8.       On the Security tab, click Add.

9.       Click Object Types and make sure that Computers is selected, and then click OK. Then, under Enter the object name to select, type the cluster name account, and then click OK. If a message appears, saying that you are about to add a disabled object, click OK.

10.   Make sure that the cluster name account is selected, and then, next to Full Control, select the Allow check box.

  

Please find the below Screen shots.