Some of your answers are incorrect. An oral stop can be unreleased when it occurs in of another .
Alveolar flaps take the place of in an intervocalic position.
Intervocalic means vowels. Flaps replace voiced and voiceless oral alveolar stops after a vowel and before an unstressed . Vowel lengthening is caused by a certain environment. In English a vowel is lengthened when followed by a voiced . Vowel length does not change the meaning in English, therefore, it is not .