Hi,
Yes, latest agent is 24.0 in the market . You can move from 11.x to 24.x via upgrade.
However please take a look at the support matrix to see the OS versions supported. Same is true for 12.1 or 12.1 SP1
https://techdocs.broadcom.com/us/en/ca-enterprise-software/intelligent-automation/workload-automation-system-agent/24-0/release-information/ca-workload-automation-system-agent-platform-support-matrix.html
Hope it helps!
Ravi Kiran