Is it possible that I will be exposed for a past sin, despite my repentance and not having disclosed it, and could persistence in it or turning away from Allah’s verses be a reason for that, especially since I hid it from people, but not from Allah?

Praise be to Allah, who has blessed you with the desire for beneficial knowledge. So proceed on your path, for the virtue of knowledge is immense, and beware of the whisperings of Satan. If you repent sincerely from your sin, Allah will accept your repentance and forgive you, even if the sin is repeated, as stated in the Hadith Qudsi: "Do what you wish, for I have forgiven you," meaning that as long as you sin and then repent, Allah will forgive you. You must have a good opinion of your Lord and not preoccupy yourself with the whisperings of Satan, for Allah accepts the repentance of every penitent. Know that good deeds erase bad deeds, and seeking knowledge is one of the greatest good deeds.