According to research impaired structural brain development due to visual deprivation from birth is not fully reversible and limits functional recovery. So even if eye sight is fully restored, cortical function will not be able to fully take advantage of that.
Experiments and studies have shown that this might be due to the fact that the visual cortex will take over a similar role in blind people as it does for people with intact eye sight. The brain uses different sensory inputs in that case and the visual brain structure is not restored after eye sight recovery.
This is still an ongoing field of research of course, but so far congenital blindless seems to be incurable, regardless of whether the sensory apparatus could be restored or replaced. Note that this only means seeing like a non-blind person. Some limited visual perception is still possible, just not "normal" sight.
Do you have some links handy? I'd be very much interested in the description of experience from people that have gained sight after congenital blindness.
You might be interested in searching up "strong critical periods" in brain development - this phenomenon has been studied for decades and has interesting implications for lots of aspects of brain development: https://en.m.wikipedia.org/wiki/Critical_period
If you are young enough, yes. But after a while, the neuroplasticity is simply not enough. Seeing is a complex enough process, if you miss learning it in your childhood, the train is gone. This is a very common error people make, announcing implant technologies to grown blind people as if the cure was just around the corner. It isn't. You will never adapt to a point where the vision you just gained is actually useful. Imagine trying to learn to read print, at 30, with a pixelated implant? It is a naiv pixie dream of sighted people.
