how to Take Backup and Restore web Application using STSADM

Hi 

 

how to take Backup and restore SharePoint WebApplications for moss 2007 using stsadm connamds.

 

example:

current Webapplcation: Https://abc/test.aspx

New webApplication: Https://newabd/test.aspx

 

Query is..

Can we get all the activated .wsp files /features /solution if we backup only siteCollecion..? Or need to backup with this backup webapplication..?

 

Or 

If we take backup only purticular SiteCollection and restore in new webapplication will it get copy all the .wsp/features/solution in to new site ..?

 

Kindly assit me.