Learn Hardcore Russian: Откуда ты привёз сувениры?

Откуда means from where. It asks about the origin point of an action or object. It cannot be replaced by Где, which only asks where (location) without specifying movement from that place.

Why is the verb привёз used here and what does it imply about the time and completeness of the action?

Привёз is the past tense of the perfective verb привезти (to bring). Using the perfective past:

Places the action in the past.
Emphasizes that the bringing is completed (you have already brought the souvenirs).
The imperfective counterpart привозил would imply a repeated or ongoing action rather than a single completed event.

Why is the form привёз masculine singular? What form would a female speaker use?

In Russian past tense, verbs agree with the subject in gender and number. Привёз is masculine singular, so it indicates that ты refers to a male speaker. A female speaker would use привезла instead of привёз.

Why is ты used instead of вы, and how would the sentence change if we switch to вы?

Ты is singular informal, used with friends, family or peers. Вы is either plural or formal singular. To make the question more polite or to address multiple people, you would say:
Откуда вы привезли сувениры?

What case is сувениры in, and why does it look the same as its nominative form?

Сувениры is in the accusative plural, because it’s the direct object of привёз. Since сувениры is an inanimate noun, its accusative plural form is identical to its nominative plural: сувениры.

What is the base verb of привёз, and what role does the prefix при- play?

The base is везти (to transport, to carry by vehicle). The prefix при- adds the meaning “towards the speaker’s current location.” So привёз literally means brought (here).

Could we use the verb принёс instead of привёз, and what would be the nuance?

Yes. Принёс (from принести, to carry on foot) emphasizes carrying by hand or on foot. Привёз often implies transportation by vehicle. In casual speech they can overlap, but that nuance exists.

Can we drop the pronoun ты and still ask the question?

Yes. Russian often omits subject pronouns when the verb form makes the person clear. You can say Откуда привёз сувениры? and it still means Where did you bring the souvenirs from?