Thank you, 1. As long as the myopia is progressing there is an opportunity to slow that and avoid complications of high myopia. While screen altering may in principle go beyond the effectiveness of optical devices for myopia control as we can provide arbitrary input to the retinal neural network, realistically myopia reversal for adult humans is not considered achieveable. Intervention should ideally be started as soon as possible. In fact there is the possibility of delaying the onset of myopia or fully preventing it for some future generations, but obviously we are a long way off from there in terms of clinical studies.

2. I think undercorrection is somewhat related. I have not yet read the study you linked, I usually refer to this review for undercorrection. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9213207/ I think it would be possible to achieve some results that way as some of the studies from the review suggest, but in practice it is difficult to precisely control the amount of myopic defocus on the retina that you get that way. Most of the time you get no myopic defocus at all due to accomodation and with strong undercorrection you risk losing the visual cues to the sign of defocus, which results in deprivation myopia. I think this is the reason that MiSight contact lenses are known to be effective, while naive undercorrection has mixed results at best.