Quiz: Nonclustered Index Internals (Disk Based, Rowstore Indexes)

We're talking about disk-based rowstore indexes!

1) Which of the following will be added to a nonclustered index, if it is not already present?*
(Assume the table is NOT a heap)
2) If the table IS a heap, which of the following will be added to a nonclustered index, if it is not already present?*
3) If your nonclustered index is NOT unique, SQL Server will sneak extra information into which part of the index (if the columns aren't already present)?*
4) If your nonclustered index IS unique, SQL Server will sneak extra information into which part of the index (if the columns aren't already present)?*
5) When does SQL Server need to use a 'uniquifier'?*