Is it obligatory to repeat the ghusl if its intention was to cleanse oneself from janabah, and not to lift the major and minor ritual impurities?

If you performed ghusl (ritual bath) with the intention of purifying yourself from janabah (state of ritual impurity requiring a full bath), then your ghusl is valid and sufficient, and you are not required to repeat it. However, if your intention for purifying was merely to remove an impurity (najasa) and not to lift the major ritual impurity (hadath al-akbar), then the janabah remains. Note that mani (sperm) and vaginal discharge are considered ritually pure (tahir) according to the preponderant opinion.