Will brushing everyday and using good mouthwash prevent tooth decay?

Yes: Brushing and mouth wash will prevent tooth decay. But proper brushing and flossing are very important after each meal and at bedtime. Furthermore, having a dental cleaning every 6 months will also be beneficial.

Yes!: Yes, and flossing.

Reduce, not prevent: Many factors determine whether or not you'll get cavities. Good brushing and flossing can reduce the risk of getting cavities, but will not completely eliminate that risk.

Not necessarily: Brushing and flossing help to prevent or manage gum disease mechanically. Tooth decay is primarily a chemical process. No amount of brushing will prevent tooth decay if your diet is high in sugar/sweets or acid (soft drinks/lemonade)--especially if you take meds that dry your mouth--or if you suffer from gerd, or heartburn. Fluoride rinses help to increase acid resistance of the teeth.