Будете проезжать мимо, проезжайте!

I have a cupple of sentences and phrases here (20, actually...) that I might've missunderstood partially or totally:

Второй юношеский.

Будете проезжать мимо, проезжайте!

What did you think they mean?

Quote:

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Будете проезжать мимо, проезжайте!

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It’s a sarcastic distortion. When Russians say goodbye, they may say:
«Будете в наших краях, заходите [в гости]» or «Будете проезжать мимо [нашего города, нашего дома], заходите [в гости]».

So, when Russians hear the first part of this sentence, they expect an invitation. But speaker are crushing their expectation: «Будете проезжать мимо [нашего дома], проезжайте [мимо/дальше]».

Thank you!

Второй юношеский. I understand the words, but I don't understand what it means. Sports, championships?

Второй юношеский [что-то; турнир, например].
"Второй" and "юношеский" are adjectives, so context is needed.

The context is - bad guy tries to make complicated push-ups. Good, but tough guy goes:

"Смотри, аккуратней, с непривычки!" (Be careful, you're out of practice???)

Bad guy does his complicated push-up anyway and then says: "Второй юношеский..."

And that's it. So I figured he was referring to some sport's thing from when he was younger.

второй юношеский разряд (по какому-либо виду спорта)