They're not stupid questions but I do wonder if they might somewhat pointless questions. You seem to be looking for an absolute rule that you'll be able to apply to every sentence in every situation. English doesn't necessarily work that way. There are differences between the variants and context will almost always help. We've asked you to use real-life situations and to give us full context. If you're having trouble understanding what that means, here's what post #1 should have looked like (assuming this was a real-life situation):
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I was at a hotel last night with a group of friends when a man entered the lobby of the hotel. I thought I recognised him but couldn't immediately work out where from. I thought about it a bit and finally realised that I had seen him before - I met him at a party back in December! This morning, I was telling my work colleague what had happened but I don't know which of the following I should say:
1. We were at hotel yesterday and a guy came in I suddenly recognized him because
I'd seen him at party before.
2. We were at hotel yesterday and a guy came in I suddenly recognized him because
I saw him at party before.
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@the batman learner Can you now see what we mean by
context?