прошедшая жизнь is a combination that is seldom used to describe the span of life that has passed already. "Past" is usually translated as «прошедший» when you are talking about grammatical tense (прошедшее время, настоящее время, будущее время). Your previous incarnation (metaphorical or real, if you believe in reincarnation) is «прошлая» жизнь.

In poetry or similar contexts. Placing declined forms of adjectives before a noun is a serious business in Russian. We rarely use inversion here IRL, even though it is commonplace in songs an poems.

Последняя жизнь means Final life/The last life.