I have lost EC2 Instance key pair and can't i download it again from AWS Management console.?
Please advise how i can connect the same instance again with easiest way?
There is no way to recover a lost keypair. In addition to the suggestion from @E.J. Brennan, there is another way to get access to your instance without recreating it via a snapshot.
Stop the instance, and disassociate the boot disk from the instance. You can then associate the volume with another instance, mount it, and you have access to the file system.
Update the authorized_keys in /home/ec2-user/.ssh, and then revert the steps - disassociate from the temporary instance, associate it with the original instance, then restart the original.