A couple of things here:
Could I still pass/walk through Ponte Sant'Angelo even if I walk the
reversed route of the pilgrims?'
As I stated earlier, the protected 'path' for the final leg to the basilica does not include Ponte Sant' Angelo. The bridge is part of the pilgrims route from other churches but will not be closed to regular pedestrians. And to my knowledge, there are no regular 'vendors' other than street peddlers and a number of beggars on that bridge, or we've never seen any, anyway.
Is the whole Villa della Conciliazione is closed?
As I also stated earlier, there are businesses and shops along Via della Conciliazione. Only PART of it will be devoted to the registered path. The rest will be open to regular pedestrians.
Is the whole Villa della Conciliazione is closed? May I know which path is closed due to the event?
The reply you received (below) seems to confirm what has been published in Vatican press releases and other news articles.
All paths are open to the pilgrims by foot. But you can see the holy door *only** if youโve registered before.*
While somewhat ambiguous, my take on it that indeed, no route is "closed" but you can only access the Holy Door via the specially constructed path that requires registration. In a word, that specific route IS closed to pedestrians whom have not registered. It does not take up the entire street to the basilica so visitors/locals can access businesses, and the church through the normal entryway.
They also do not confirm that "that" path is a two-way route, only that normal access to Via della Conciliazione and the bridge is possible.
As far as your registration, it should " confirm the request for the pilgrimage and indicate the best time to arrive at the beginning of the protected pathway. This system will reduce delays to the minimum, and help to guarantee an atmosphere of prayer and welcome during the pilgrimage on foot to the Holy Door." ( from "Vatican Insider"). I'm guessing it will also indicate where you need to arrive. If not, there will be a Welcome Center at Via Della Conciliazione, 7. That office will also provide same-day registration for pilgrims whom have not submitted a form in advance. This can be your back-up if your passes fail to arrive in the mail before you leave although there is likely to be a queue of others doing the same thing.
Just my take on all of this, anyway.