How do I know that I am using the last API version ?

The bank will take care via the bank community manager and API product owner of the availability of the API products. The publication of new version or any update in general will be officialy communicated via the newsletter and the news feed feature of the developer portal. 

Who can I contact in case of issue with keys?

The best way to solve an issue on key management and rights management is to contact the bank via the "contact feature". Please identify yourself properly in the contact form, as well as the reason for contacting so that the message can be forwarded to the right addressee.