Is this sentence a passive voice? (was=aux) (born=p.p of bear)
Yes, 'was' is the auxiliary verb, and 'born' is the past participle of the main verb
Is born a verb or an adjective? (was=main verb) (born=adjective)
It's a verb in the past participle.
What is the tense of this sentence? is it present simple?
It's a past simple tense in the passive voice.
The verb is to 'bear', which means to carry. The past simple is 'bore' and the past participle is 'born'.
The active form of this past simple sentence is:
My mother bore me.
We don't use this form any more, because the subject of the active sentence (my mother) is somewhat unnecessary - it is obvious that it was your mother who gave birth to you, so we don't need to say it. Instead we put the emphasis on the person who was born by their mother, and use the passive form of the sentence - I was born.