A:
The Salah you miss due to sleep or forgetfulness should be offered the moment you wake up or the moment you remember. It does not matter if you wake up or remember it after sunrise. This is based on the Hadith in which the Prophet (peace be upon him) said:
Anyone who misses a Salah because of sleep or forgetfulness should offer it when they remember it; there is no Kaffarah (expiation) for it except this.
As for the Salah you intentionally abandoned while believing in its obligation, according to the more correct of the two scholarly opinions such an act constitutes major Kufr (disbelief that takes the Muslim out of Islam). (Part No. 6; Page No. 11) You should not make up for it, but you have to repent to Allah, seek His Forgiveness, and regret abandoning it. You should observe the Five Obligatory Daily Prayers regularly. This is based on the Hadith in which the Prophet said:
The covenant that distinguishes between us and them (the disbelievers) is Salah. Anyone who abandons it has committed Kufr (disbelief).
Another Hadith states:
Between a servant and Shirk (associating others with Allah in His Divinity or worship) and Kufr is abandoning Salah.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.