I don’t know the answer to your first question, but to the second – yes, it does depending on the disposition of the person (as with any plenary indulgence).
I believe the origin of this can be found in Holy Scripture. Note what the link on footnote 7 reads.
14 Is anyone among you sick? 6 He should summon the presbyters of the church, and they should pray over him and anoint (him) with oil in the name of the Lord,
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