There will be no central server to store every E-ID that was registred. They will be stored only on the phone of the individuals themselfes.
No. There is no direct restrictions in the new law. But unneeded use can be brought to a court. So I could Imagine that central services like the SBB will not be able to request this data.
Maby they can request if you are over 16 or not, which would be an improvement to today, where one has to put name and birthday to buy a ticket online.