(1) What is complete teshuvah? One who has the opportunity to transgress with a thing they have done before, but separates themselves from it and doesn't do it because of teshuvah, not out of fear or lack of strength.
For example: Someone slept with a woman sinfully, and some time later, he finds himself alone with her, and he still loves her, and his body is able, and he is in the same country that he sinned in before - if he parted without sinning, that is complete teshuvah.
Of such Solomon said: "Remember then thy Creator in the days of thy youth" (Ecc. 12.1). Even if he made no reparation save in his old age, at a time when it was already impossible for him to repeat his misdeeds, although it is not the best repentance, it still is of help to him and he is considered a penitent. Moreover, though he continued a life of sin but did repent on his dying day, and did die a penitent, all of his sins are forgiven, even as it is said: "While the sun, or the light, or the moon, or the stars, be not darkened, nor the clouds return after the rain" (Ibid. 12.2), yea, that is the day of death. Deduct herefrom that if he remembered his Creator and did repent ere he died, he was forgiven.1Ibid. 86b; Kiddushin, 40b; Shabbat, 151a. C.