You didn’t do too bad...classification or security clearance levels range from Confidential, Secret, and Top Secret. The lowest I’ve ever worked with is Secret, but technically a Confidential clearance would be the lowest (just never seen it in use).
Caveats and need to know are the keys here which are additional restrictions/conditions placed on access to classified information. These can include details about the specific type of information or the context in which it can be accessed. For instance, Sensitive Compartmented Information (SCI) is a subset of classified data that involves sensitive sources or methods, requiring special handling procedures.
Special access programs (SAPs) are HIGHLY controlled access programs that provide additional security measures beyond anything mentioned above…and are designed to protect exceptionally sensitive information. Additionally, these programs can be acknowledged or unacknowledged (by Congressional oversight programs). I’ve had access to several of these and yet there are still hundreds I’ve probably never even heard of much less had access to.