meaning - So, in 5 minutes means either during 5 minutes or after . . . With respect to your paraphrase: during five minutes, during five weeks, etc are not idiomatic as is When using the preposition during with a number of time-units, you need a noun, the span, that comprises those time-units: "during a space of five minutes" or "during a brief respite of five weeks" or "during three weeks of the semester"
5 years experience in or 5 year experience in or 5 years of . . . Here are some facts would make it more clearer: Years are countable so using 5 years would be correct Oxford dictionary says: [countable, usually plural] age; time of life -He was 14 years old when it happened -She looks young for her years -They were both only 20 years of age -A twenty-year-old manHe died in his sixtieth year -She's getting on in years (= is no longer young) Experience
Does “Children under 8 years old” include “8 years old?” Is the sentence "children under 8 years old" means 0-8 or 0-7? as I understand, less than 8 does not include 8 How about "under"? I just think about "under" as similar as "less" so I just think it