Movement from Default semantic model to Custom semantic model

Hello,

As part of our development activity, we had created around 9 tables and 9 views in Fabric Warehouse and all tables and views are part of Default semantic model. Using Default semantic model, we had created 6 reports. Now, we want to implement Row Level Security (RLS).

Question # 1 - Can we implement RLS on Defaultsemantic model?
The reason for asking this question is because we are not getting Open data model option for Defaultsemantic model. We had already Turned on "Users can edit data models in the Power BI service (preview)" in Workspace settings. And we think that without Open data model view, we won't be able to implement RLS.

Question # 2 - How will we move Tables and Views from Default semantic model to Custom semantic model?
The reason for asking this question is because we are not allowed to select few of the views while creating Custom semantic model.

Question # 3 - How will we change PowerBI reports to start using Custom semantic model instead of Default semantic model without having need to recreate the entire report?