Does committing sins and then repenting with all its conditions guarantee forgiveness, and is intense remorse over them a form of whispering (waswas), punishment, or trial?

Rejoice, for as long as you have regretted and repented to Allah Almighty, you are on the path of good. Increase your acts of seeking forgiveness (Istighfar) and perform the prayer of repentance (Salat al-Tawbah). Trust in Allah's promise to accept the repentance of those who repent and seek forgiveness, for He says: "And indeed, I am Forgiving to whoever repents, believes, and does righteousness, and then is guided." (Qur’an 20:82) And He says: "And whoever does evil or wrongs himself then seeks forgiveness of Allah will find Allah Forgiving and Merciful." (Qur’an 4:110). In the Hadith Qudsi, Allah says: "O son of Adam, as long as you invoke Me and place your hope in Me, I will forgive you for what you have done, and I do not care. O son of Adam, were your sins to reach the clouds of the sky and you then sought My forgiveness, I would forgive you." Turn away from dwelling on thoughts instilled by Satan, lest he drags you into despair of Allah's mercy.