(V.25:68)
A) See the footnote of (V.2:22).
B) See the footnote of (V.4:135).
(V.25:70) Islam demolishes all the previous evil deeds and so do migration (for Allah’s sake) and Hajj (pilgrimage to Makkah). [Al-Lu’lu’ Wal-Marjan, Vol. 1, Chapter 52, Page 205]
Narrated Ibn ‘Abbâs رضي الله عنهما: Some pagans who committed murders in great number and committed illegal sexual intercourse excessively, came to Muhammad صلى الله عليه وسلم and said: "O Muhammad! Whatever you say, and invite people to, is good, but we wish if you could inform us whether we can make an expiation for our (past evil) deeds." So the Divine Verses came: "Those who invoke not with Allah any other god, nor kill such person as Allah has forbidden except for just cause, nor commit illegal sexual intercourse." (V.25:68) "...Except those who repent..." (V.25:70).
And there was also revealed: "Say: O My slaves who have transgressed against their ownselves! (by committing sins), despair not of the Mercy of Allah." (V.39:53). (Sahih Al-Bukhari, Vol. 6, Hadîth No. 334).