I just bought an Ipad on 26/11 and I just realised that it is the Ipad 3rd Generation not the 4th so can I still replace it?

You only get 14 days from date of purchase (or date of delivery for online orders) to return it for full refund, if bought direct form Apple. Other stores will have their own return policy.

If you got it from Apple you are now on day 15, so if you were to go down and plead your case, who knows? Maybe you could convince someone to give you a break, just do not count on it (but no harm in asking).

Are you sure it's the iPad 3. Check the A# on the back of the iPad.

Identify iPad Models http://support.apple.com/kb/HT5452http://www.apple.com/ipad/compare/

 Cheers, Tom 😉