Is it a condition to carry out the hadd punishment on me after my repentance from a major sin I committed, and does this necessitate presenting myself to a judge and being seen by a group of people?

If what is meant by major sins is adultery (zina), then it is one of the greatest abominations, and the Qur'an warned against it. Whoever has been afflicted by it and has not had the hadd punishment applied to them, then they must perform sincere repentance (tawbah nasuh). They must also conceal their sin, based on the Prophet Muhammad's (peace be upon him) saying: "Whoever is afflicted by any of these abominations, let him conceal himself with the concealment of Allah, Exalted and Glorified be He." The person who committed the sin must know that Allah forgives all sins if the repentance is sincere. Among the conditions for sincere repentance is the firm resolve not to return to the sin, to distance oneself from its incitements and bad companions, and to replace them with righteous ones. If what is meant is theft, then fatwa number 57260 can be consulted. In general, a person must hasten to perform sincere repentance for any sin they have committed, for if they repent, Allah will accept their repentance, no matter how great their sin.