Just one correction:
Non-leaf level entries contain only index key columns and the pointer to a lower level page. Included columns only exist in the leaf level entries; they are not carried in the non-leaf level entries.
Non-leaf entries of a nonclustered index contain the index key columns, a pointer to the page below and, if the index has not been declared as unique, it will also contain the clustered index key or RID (depending whether the base table is a heap or clustered index). This ensures that there are never complete duplicate rows in the upper level of a nonclustered index
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