Hi Rafael.
To figure out which release you're working with, just do this : SAP menu -> System -> Status
Under Component version, here you can know which version you SAP system is working under. If you want to go ahead and know the release of each component just click the button just under.
SAP Basis component has the same release version as your SAP system.
When you ask what SAP version is suited for my experience, it's such a large question. As SAP is not a system, but a company and a large set of systems and solutions.
I'll rather answer the question, what SAP ERP version is suited for your experience. The best thing is to have more knowledge about the last release. As I know it's the ECC6 with Ehp6(Enhancement Package).
For ABAP, it's not a big deal, as releases doesn't change a lot from release to release. But just to be clear. ABAP is a component of Netweaver, and not ERP. So changes may happen (I'm not sure if it happened last years with Netweaver new releases) when Netweaver release a new version.
Hope this will make things clear for you.
Regards
Ab.Sidr (Salah)