Learn Russian: Кот то поцарапает мне руку, то испачкает мне диван. - The cat first scratches my hand, then stains my sofa.

This is the dative of possession and detriment. In Russian, when an action affects your body parts (like руку) or personal belongings (like диван), especially in a negative way, we use the dative pronoun (мне) for the person affected. It literally feels like 'scratches the hand on me' or 'stains the sofa on me,' emphasizing that you are the victim of the cat's actions.

What is the meaning of the repeated то ..., то ... in this sentence?

The paired conjunction то ..., то ... expresses alternating actions, meaning 'now this, now that' or 'first this, then that.' In this case, it highlights the cat's unpredictable and annoying behavior, jumping back and forth between scratching your hand and ruining your sofa.

The translation uses present tense ('scratches', 'stains'), but поцарапает and испачкает are perfective verbs in the future tense. Why?

When used with то ..., то ..., perfective future verbs often describe habitual, recurring, or alternating actions. It gives the sense of 'one moment he will do this, the next he will do that.' While Russian uses the future tense to show the completion of each alternating event, English naturally expresses this kind of ongoing habit in the present tense.

If I said поцарапает мою руку instead of поцарапает мне руку, would it be wrong?