Were there any independent mujtahids after the four Imams, and how does a mujtahid advance through the levels of ijtihad?

No era is devoid of a Mujtahid (a qualified scholar capable of independent legal reasoning) who establishes proof, supports the Sunnah, and condemns innovation. This is based on the Hadith: "A group from my Ummah will continue to be upon the truth." Al-Dhahabi mentioned that Ibn al-Arabi reached the rank of Ijtihad. Al-Mardawi and Al-Karmi stated that Ibn Taymiyyah reached it. Al-Shawkani, Al-Sakhawi, and Ibn al-Imad mentioned that Ibn Abd al-Salam, Ibn Daqiq al-Eid, and Abu Shama reached it. The transition of a Mujtahid between different levels depends on their depth of knowledge and their mastery of the conditions for Ijtihad.