In another question, I asked about why I feel scrum turns active developers into passive developers, and it seems that the overall problem is not scrumy (related to scrum), and rather it's related to the bad implementation of scrum. So, here I have some questions about the scope of the responsibilities of PO (product owner) and the limitations he/she shouldn't pass.

1. Should PO interfere the UI design, when there are designers at work in scrum team? (an example of this which has happened to us, is to replace checkboxes with a drop down list with two items, namely, yes and no; or to make some boxes larger, or to left-align some content instead of centering them on the page, or stuff like that). If yeah, to what extent? Colors? Layout?
2. Should PO interfere in Design and architecture of coding? This hasn't happened to us yet, but I'm really curious about the boundaries. For example does PO has the right to change the platform (moving from ASP.NET MVC to PHP, or something like that), or choosing the count of servers (tier architecture), etc.
3. Should PO interfere in validation mechanisms? For example, this field should be required, or we don't need to get this piece of information from user. Sometimes, analyzers and designers confirm that something can be handled behind the scene, like extracting the user profile info from another source, instead of asking for it in UI.
4. How granular could/should PO get into the analysis and design? For example, a user story might be: "As a customer, I'd like to be able to buy new domains online". However, scrum team can implement this user story in a wizard of five steps, or in one single page. To which level PO should monitor, or govern, or supervise the technical analysis, design, and implementation?

I asked these questions to judge whether our implementation is right or wrong?