Learn Russian: Прежде чем сделать выбор, я долго обдумываю все варианты. - Before making a choice, I think over all options for a long time.

When the subject is the same for both actions (here, я does the thinking and the choosing), Russian uses the infinitive after прежде чем. If the subjects were different, you would need a conjugated verb in the past tense, like прежде чем он сделал выбор (before he made a choice).

Why is the perfective verb сделать paired with the imperfective verb обдумываю in this sentence?

They describe different types of actions. Сделать is perfective because making a choice is a single, completed result. Обдумываю is imperfective because it is an ongoing, extended process, which is emphasized by the word долго (for a long time).

Is there a difference between прежде чем and перед тем как? Can I swap them here?

Yes, you can swap them, and the grammar remains exactly the same. Прежде чем is slightly more formal and emphasizes a logical sequence (the thinking must logically precede the choosing). Перед тем как is more neutral and is very common in everyday conversation.

The English translation uses both "choice" and "options". What is the exact difference between выбор and варианты in Russian?