YES. Generally antibiotics make oral contraceptives less effective. It is recommended to use 'a back up method' from the 1st dose of antibiotic to the 'end of the pill pack'.
No with ExceptionOF2. It used be considered by some in the past but the research has shown that it does not in reality. With exception of Rifampin type Antibiotics there no conclusive evidence that commonly prescribed Antibiotics make hormonal BCPills less effective Only exceptions are rifampin and Rifabutin.
YES. Yes potentially diminish the effectiveness of oral contraceptives so use additional protective measures.