Data is not stored in layouts. Data is stored in the tables on which the layouts are based. Your two layouts can be based on the same table or different tables. Apparently, your two layouts are based on different tables.
Is there any relationship linking the two tables?
1) Why is it necessary to duplicate the same data in both tables? This is sometimes necessary, but other times indicates an unnecessary duplication of your data that is best avoided.
2) Then what should happen if a duplicate is not added to layout 1? Do you mean that a record should be created in #2 regardless?
3 & 4) Why would a record ever fail to be inserted?