NO, you don't need a prescription for pure oxygen if you get industrial grade oxygen vs. medical grade oxygen. Their purity are the same. You need to find a source for industrial grade oxygen in your area; look under welding because welders need pure oxygen for their welding. I got mine locally and the source provided its own steel tank, which I needed to buy, plus the oxygen. Thereafter, I just need to pay for oxygen refills.
Inhaling ozone can be very irritating to the lungs and can cause scarring if inhaled too much and for extended periods of time. That's why an oil bubbler is needed if you are going to inhale ozone. The oil will break down the ozone to components that your lungs can tolerate.
Your GI tract can tolerate ozonated water.