1. My brother usually has some rice for dinner, but now he has instant noodles.

Corrected: The verb "have" should be used consistently in the present tense.
2. She promised to phone me after dinner.

Corrected: The verb "promise" should be in the past tense to indicate a past action.
3. Is Peter going to read comic books tomorrow?

Corrected: The sentence should be in the future continuous tense to indicate a planned action.
4. Where are you going next weekend?

Corrected: The verb "are" should be used instead of "you going" for correct grammar.
5. Did you have a good time last weekend?

Corrected: The sentence should be in the past simple tense to refer to a specific time in the past.
6. The weather is fine, so we can go out with friends.

Corrected: The sentence should use the present simple tense to describe a current situation.
7. We collected stamps when we were children.

Corrected: The verb "collected" should be in the past simple tense to indicate a past action.
8. We have been collecting stamps since we were children.

Corrected: The sentence should use the present perfect continuous tense to indicate an action that started in the past and continues to the present.
9. These students have been learning English for five years.

Corrected: The sentence is already correct.
10. Liz hasn't sent us any letters since she moved to the USA.

Corrected: The sentence should use the present perfect tense to indicate an action that started in the past and continues to the present.
11. He has had a cold since last Sunday.

Corrected: The sentence is already correct.
12. They have already finished their work.

Corrected: The sentence is already correct.