Hi Henk,
How about adding restricted access rules to both of them? 
If you also click the 'eye' icon next to the restrict access rule, it will be hidden from view for the students. This way the views will be:
No activity completed ==> both visible
V1.0 completed ==> V2.0 hidden from view
V2.0 completed ==> V1.0 hidden from view
A third activity could be restricted in the sense that students would have to have completed either V1.0 or V2.0 by adding Access restriction Rule 1 or Rule 2.
Hope this helps!