You need to run isql -v at the command line to really know which OpenClient (ASE SDK) version you are running.
SQL Advantage is loooooong gone. It was the GUI interface for ASE in the 11.x days. Some customers used it in the 12.x days.
Today it has been (and should be) fully replaced with DBISQL as a gui. DBISQL runs on any Java platform and is part of the current ASE PC Client/SDK.
I would also avoid using older ODBC drivers. Current drivers are really 2 parts - 1) the wire-level protocol driver - ODBC, jConnect, etc that does not require an OpenClient layer and 2) the metadata stored procedures that come with the driver and should be installed on the ASE server they are connecting to.
You can also use current ASE SDK client to connect to ASE 12.5. They are backward compatible, where as the older 11.x based-drivers (and SQL Advantage) may not be able to understand even 12.5 server capabilities (e.g. datatypes and @@pagesize > 2048).
Chris