5. Is it possible to make events/CRFs dependable on the subject group, for instance in case of a study with different study arms?

Preparation Phase : Build Study in Sandbox

The only way to achieve this at the moment is by adding an item on the first CRF of the study, asking for the treatment (arm). Depending on the answer you can build rules that hide/show questions on the appropriate CRFs. It is not possible to hide complete events or CRFs.