Hello Chandra
Take a look at this lessons to have most of your questions answered concerning GNS3 content and labs:
Keep in mind that the GNS3 software is free, but you’ll have to supply the IOS images yourself. Cisco owns the copyright on IOS so it can’t be shared freely. You’ll have to purchase them, or get them from someone who has legal access to them.
You can also take a look at Rene’s site GNS3Vault specializing in GNS3 labs for Cisco certifications You’ll find a lot of useful information there:
I hope this has been helpful!
Laz