Is a person considered an infidel if he does not pray two rak'ahs after ghusl upon entering Islam, despite believing in everything Islam decrees and being ignorant of this condition? And is the non-acceptance of his deeds during that period due to his ignorance and not his stubbornness?

For one to embrace Islam, it suffices to pronounce the Two Testimonies (Shahadatayn) and firmly believe in them. Neither ghusl (ritual bath) nor the two rak'ahs (units of prayer) thereafter are conditions for the validity of Islam. The preponderant opinion is that ghusl is recommended, and this is supported by the fact that a large number of people embraced Islam, and it was not narrated that they were commanded to perform it. Mu'adh did not command the people of Yemen with it when he invited them to Islam. Therefore, omitting ghusl and the two rak'ahs does not affect the validity of Islam or the acceptance of the deeds performed by the Muslim. Faith has multiple branches; some branches, like the two testimonies, if removed, faith ceases to exist. Other branches, if removed, faith does not cease to exist. Omitting supererogatory acts (sunan), recommended acts (mustahabbat), some obligatory acts (wajibat), and committing disliked acts (makruhat) and major sins (kabair) does not remove a Muslim from the core of faith. He should, however, strive to ascend the levels of perfection.