Try not to question your diagnoses too much - there is quite a bit of overlap between Bipolar symptoms and Borderline a Personality Disorder symptoms. It's actually quite common to get a diagnoses of one or the other and then to have it changed (misdiagnoses).

Psychosis is possible with Borderline Personality Disorder and that can include auditory and visual hallucinations. However, it is important to note that you don't really get "mania" with BPD as you do Bipolar Disorder and the mood changes in BPD are more commonly very rapid, often multiple times during a single day (possible in Bipolar Disorder but it's rarer occurrence than it is in BPD).