Q1. Why are these counters like 人(にん), 日(にち) and 歳(さい) not universal?
- 人(にん) is impossible to be joined with 1(いち) or 2(に)?
- 日(にち) is impossible to be joined with 2, 3, 4, 5, 6, 7, 8, 9, 10, 14, 20 or 24?
- 歳(さい) is impossible to be joined with 20(にじゅう)?
Q2. When do we read 7 and 9 as "しち" and "く" rather than "なな" and "きゅう"?