Is reading a surah from the Holy Qur’an collectively online, followed by supplicating for one another in the unseen, considered a gathering of remembrance (halqat dhikr), and will the supplication thereafter be answered?

The apparent meaning of the evidence regarding the virtue of gatherings of remembrance (dhikr) pertains to those who gather in one place, not those who are dispersed. This includes the hadith about the roaming angels who seek out gatherings of remembrance and encompass those present, and Allah forgives them due to the blessing of their gathering, even someone who merely passes by and sits with them.

The hadith indicates the virtue of attending such a gathering, even if the person was not originally among those engaged in remembrance, and that their companion is included in the virtue, out of honor for them.

It also points out that gathering together for obedience and the Sunnah in one place has an effect on obtaining virtue, and that proximity and gathering are intended by the Sharia.

As for the supplication being answered after an act of obedience, there is no explicit text stating this. However, the gathering of Muslims in remembrance circles is among the times when supplications are answered.