Please help me with this

Can someone answer this pls ill give brainliest both ser and estar mean ‘to be’. in what situations do we use estar? estar, venir, and ir are considered irregular verbs. what makes a verb “irregular”?

Which word correctly completes this question? ¿ características tiene el teléfono celular? a. quién b. qué c. cómo d. por qué

Decide if the following sentence is grammatically correct or incorrect. cuando nosostros iban de vacaciones sale todo mal.