Student or Learner
The words #1 and #2 are given in the Longman dictionary, but the others are not.
twentysomething - Definition from Longman English Dictionary Online
thirtysomething - Definition from Longman English Dictionary Online
Anyway, the words #3 to #8 exist, don't they?
市場調査報告書：ベビーブーマーと飲食品業界：米国 - 目次
30% of Fortysomethings Use Natural/Organic Foods
Yes. The use of " - something" as a suffix didn't really become mainstream until the TV show thirtysomething became a hit. But it's fairly common usage to say (for example) "My grandpa is 80-something" when you can't remember his exact age, or to answer "forty-something" if you're 49 and don't want to admit your exact age.