1. QlikView cannot write back to a db out of the box, it hasn't been designed for that. you can however do it using an extension object (K4 analytics or SQL writeback comes to mind)
2. I don't think its possible to stop bookmarks from being created. When a user creates a bookmark, only that particular user can see and use it. it can also be shared to others users , this is a controlled by the 'allow creation of server objects' flag in the QMC.
3. This is a Qlik community, so i am obviously going to say Qlik.I have no experience with Tableau
9. Drilldowns a group of fields in a hierarchy that are predefined by the developer, i.e. Country, City, Town. The user can then click on a Country which will then display the Cities relating to that country and so on.
Cyclic groups are also predefined, you can group a number of fields together and by clicking the cyclic icon you can change the dimension to each of the values in the group in turn. Cyclic groups can also be used in expressions, i.e. you could have Sales Value and Sales Quantity in a cyclic group expression, then you can cycle the expression on each of them