Is it required to run IDXACTIVATE when adding an index to an existing table when the database is offline?

Is it required to run IDXACTIVATE when adding an index to an existing table while the database is offline? 
Is it required to run IDXACTIVATE when adding an index to an existing table when the database is online?
Is it required to run IDXACTIVATE when adding an index to an existing table using a delta.df when the database is online? 
How is the newly added index updated with the existing data, if an IDXACTIVATE is not used?
 

IDXACTIVATE can be used to activate inactive indexes, regardless if they were added online or offline. 

IDXACTIVATE can be used if an inactive index is added to an existing table when the database is offline/online.

If the index is added as active, then there is no need to use IDXACTIVATE to reactivate it.
Using IDXACTIVATE to activate an already active index will give the following error: "Index Activate: cannot activate an active index. (12805)".

When an index is added as active by loading a delta.df or created using the Data Dictionary tool, the newly created index is update automatically with the existing data in the table by the Data Administration Tool. 

References to Other Documentation:
Database Administration: PROUTIL IDXACTIVATE qualifier

Progress Article(s):
 What is IDXACTIVATE?
 Best way to add new index to table with large count of records?