When a stack is in the UPDATE_ROLLBACK_FAILED state, you can continue rolling it back to return it to a working state (to UPDATE_ROLLBACK_COMPLETE). You cannot update a stack that is in the UPDATE_ROLLBACK_FAILED state. However, if you can continue to roll it back, you can return the stack to its original settings and try to update it again.
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks- continueu pdaterollback.html

This is the complete list of CloudFormation Helper Scripts: cfn-init, cfn-signal, cfn-get-metadata, cfn-hup
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-helper-scripts- reference.html

Explanation
The AWS Documentation mentions the below
Each layer has a set of built-in recipes assigned to each lifecycle event, although some layers lack Undeploy
recipes. When a lifecycle event occurs on an instance,
AWS OpsWorks Stacks runs the appropriate set of recipes for the associated layer.
The below diagram shows a snapshot in the stack settings where you can enable custom cookbooks

For more information on automating recipe's, please visit the below URL:
http://docs.aws.amazon.com/opsworks/latest/userguide/workingcookbook-assigni
ngcustom.html

Explanation

For more information on Elastic beanstalk, please visit the below URL:
* http://docs.aws.a
mazon.com/elasticbeanstalk/latest/dg/concepts.platforms. htm I

This is the complete list of Pseudo Parameters: AWS::AccountId, AWS::NotificationARNs, AWS::NoValue, AWS::Region, AWS::StackId, AWS::StackName
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/pseudo-parameter- reference.html