Learn Swedish: Vänd dig mot spegeln. - Turn towards the mirror.

In Swedish, the verb for turning your body is the reflexive vända sig (literally to turn oneself). When giving a command using the imperative, you still must include the reflexive pronoun. Since you are commanding one person, you use dig.

How do I form the imperative vänd from the dictionary form of the verb?

The infinitive is vända. Because it belongs to verb group 2, you drop the final -a from the infinitive to get the imperative command form: vänd.

Is dig still pronounced like dej when used in a command?

Yes! The pronunciation rule does not change. Even in an imperative sentence, dig is almost always pronounced dej in spoken Swedish.

Could mot also mean against in this sentence?

The preposition mot can mean both towards and against depending on the context. Here, because of the action of turning, it clearly means towards. If you were pushing or leaning on the mirror, it would translate to against.