In the US you can only do over the counter reading glasses. Far sightedness correction is prescription only.

I think you have that backwards. Nearsightedness, the one where you can't see far, is the one that needs a prescription.

Nearsightedness (myopia) and farsightedness (hyperopia) are both not OTC, presbyopia is. However, the correction for presbyopia (+ lenses) is the same as for farsightedness, provided you don’t have a lot of astigmatism. I won’t explain the intricacies here, but you can look up how accommodation works using the terms above.

Officially yes, but in practice you can buy glasses online if you know the power of the lenses. Contact lenses do have a prescription verification requirement for sellers.

Not with Warby Parker online ordering.