Hello Chen Chuan,
Thank you for contacting Telerik support.
Unfortunately, customizing the notification message is not possible at the moment. I have logged it as a feature request, so that this would be possible in the near future.
As for the second thing you want to achieve, you would have to customize your workflow, which requires a higher Sitefinity license. Follow the link
for more information about Sitefinity licensing.
Don't hesitate to contact us if you have any further questions.
All the best,
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items