What is the difference between the questions ‘cómo estás? ’ and ‘cómo eres? ’ answer both in complete sentences. both ‘ser’ and ‘estar’ mean, ‘to be’, but when do we use each in spanish?

Como estas means how are you and como eres means how are you but meaning physically

¿cómo estás? We use this to ask someone how are they feeling, bien, mal, feliz, triste, etc. On the other hand, we use (rarely) ¿cómo eres? to ask someone how they are in appearance and personality, bonito/guapo, feo, alto, bajo, etc.

Ex1: - Hola Nick, ¿cómo estás? 
      - Hola Jhon, ¿estoy bien y tu?
      - Estoy feliz!
      (conversation continues)

Ex2: - Hola, me llamo Josh, mido 1 metro con 83 centimetros, tengo pelo castaño y ojos marrones. ¿Y tu? ¿Como eres?

Spanish is my main/native language, i might have missed some information but i think this should answer your question. :)

Can you write the question correctly?

Incorrect. the right answer is "su nieto estudia la lecciòn"