Neat to see that this is nearly "2nd day"! Kinda like how Tuesday is "2s-day". :)
I think this sentence more specifically refers to either next Tuesday or last Tuesday, but not Tuesday in general. The article you have there makes it seem much more general. But i don't know what the Russian expression would be in that case.
I can't hear the slow pronounciation, but one difference I can think of is the stress. When pronouncing words one-by-one, «во» might get a stress of its own and be pronounced /'vo/.
However, in normal speech, it doesn't have a stress of its own: «во вторник» is pronounced as a single unit, /vɐ 'ftornʲɪk/.
Most prepositions will be 'glued' to the next word, and usually they don't have a stress of their own: на мо́ре /nɐ 'morʲɪ/ 'at the sea[side]', за стено́й /zɐ stʲɪ'noɪ̯/.
(Although sometimes they can steal the next word's stress: на́ зиму ['na zʲɪmu] 'for the winter'; this is usually optional, i.e. на зи́му [nɐ 'zʲimu] is equally OK. In facts, forms with stress shifted to the pronoun often sound archaic.)
When it's followed by a voiceless consonant (кпстфхцчшщ, e.g. все ['fsʲe] 'all'), and at the end of the word (e.g. ров ['rof] 'ditch').
This is not considered prepositional case?
edit: Right, markers of time get accusitive. Thanks!
Prepositional case would be «вторнике», as in «о вторнике» 'about Tuesday'. To tell that something happens on Tuesday, you use accusative.
"По вторника" is incorrect.
"По вторник" (without the "-a") is the "to tuesday" part of the expressions like "from sunday to tuesday".
"По вторникам" means "on tuesdays".
So are во вторник and по вторникам the same?
(I never said по вторник, I said во)
Sorry, it was a typo, I meant "по вторника" is incorrect, as in "there's no such expression". Corrected.
No they are not the same. "Во вторник" means "on tuesday", "по вторникам" means "on tuesdays". The difference is "on one particular tuesday" vs. "every tuesday".