It means that Tom got on the train at eight o'clock. "Caught" just means he was there on time and made it into his seat.
Thieves will be caught.
I wouldn't be caught dead in sleeping during the class.
It is a fishing term. At first is seemed as if you were caught ( hooked ) but you escaped capture or consequence.
If something "catches" your eye, it has snagged your attention. You are focused on that thing for whatever reason.
"You threw me for a loop" means that you surprised me or that I wasn't expecting that. It could also mean it caught you off guard and you totally weren't expecting it.
This is the equivalent of our American idiom: If you fail, try try again.
It is not an idiom, it means your nose is itching.
It's not really an idiom. It means "what are you thinking about."
RFP is not an idiom. It's an abbreviation.
"Sieve" is not an idiom. See the related link.
It's not an idiom. It means the tip of your nostril.
idiom means expression like a page in a book