Are there existing modules to group nodes and give sequential access to them in Drupal 7
I would recommend the following modules:


Views: Views is a powerfull query and report generator. You can filter and sort your nodes or show individual nodes based on any criteria.
Rules: Rules allows you to take action on a lot of ocations. Let's say you can change data, roles or access rights on nodes when a user sees a node or confirms to have read the contents.
Fields (built in core): Is a little bit like Access: Create your data structures without coding.


It's very likely that you can do 90%-100% of you requirements with this (and may be some more helper) modules. Sometimes some glue code in a custom module is necessary.