Hi Swan, I think you have your rules a little mixed up. I think you are thinking of “or” - for “and”, the verb is always plural. So only #1 is correct, although bedroom is a compound noun, so “My mother and I are living in an apartment with three bedrooms.” Good luck with your IELTS - try to relax and not overthink it!
“When two or more singular nouns or pronouns are connected by or or nor, use a singular verb. The book or the pen is in the drawer. … When a compound subject contains both a singular and a plural noun or pronoun joined by or or nor, the verb should agree with the part of the subject that is nearer the verb.”
Thank you so much for your care and complete answer.
I got where I made a mistake.
My exam was awesome. I answered all the questions. It was just the speaking test and other 3 skills will be taken on 19th of Aug.