the word "never" is not in the sentence. to say "my friend never came to my house" would be "मेरा दोस्त मेरे घर कभी नहीं आया"

How I understand it is it was a plan that the friend comes and he or she did not. She or he could have come to your home another time in the past.

It's the object of the sentence. मेरा घर अच्छा है = My house is good (Subject is मेरा घर) वह​ मेरे घर आया = He came to my house. (Subject is वह​, which makes घर the object, changing it into oblique form, which makes all of its adjectives plural.)