Yes it is possible to have more then 2 steps approval.
The documentation for creation of custom workflow is here http://www.sitefinity.com/documentation/documentationarticles/developers-guide/sitefinity-essentials/modules/workflow-for-content-modules/custom-workflow please keep in mind that the custom workflow is not included in all licenses so if you decide to make a custom workflow make sure you have the right Sitefinity license.
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 Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items