Interesting topic!
I'd think your first option the most likely, based on a few quotes.
After Bilbo's departure, but before Gandalf knew his ring was the One, G. tells Frodo:
Quote:
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'But if you take my advice you will use it very seldom, if at all.
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So, he didn't expressly forbid Frodo from wearing the Ring, at least in the manner Bilbo had: to escape from nosy or annoying neighbors.
Later, at Bombadil's house, when Frodo wears it:
Quote:
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Frodo was delighted (in a way): it was his own ring all right, for Merry was staring blankly at his chair, and obviously could not see him.
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I don't read there a sense that that was the first time Frodo had used the Ring.
And in Lothlórien, much later, Galadriel tells Frodo:
Quote:
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'Only thrice have you set the Ring upon your finger since you knew what you possessed.'
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Meaning, after Gandalf's talk in
The Shadow of the Past, because it adds up: Frodo used the Ring at Bombadil's, on Weathertop, and at the Ford of Bruinen.