Must one repeat the Ghusl and the prayer if, after performing Ghusl from Janabah and praying, the worshipper discovers the presence of nail polish preventing water from reaching the nail?

Prayer with incomplete purification is invalid and must be repeated. As for an incomplete ghusl (ritual bath), there is a difference of opinion: some scholars say that it is obligatory to complete the ghusl by washing the part that was missed with a new intention if there was a long interval. Others obligate repeating the entire ghusl if there was a long interval, because continuity (muwalat) is a condition for the validity of purification, citing the hadith of the man whom the Prophet, peace and blessings be upon him, ordered to repeat his ablution and prayer due to a dry spot that water had not reached. Some scholars obligate continuity in ablution but not in ghusl. Adhering to the obligation of continuity in both ablution and ghusl is more cautious and more absolving of responsibility.