Q4. Wasim was 18 (officially!!) and that was against NZ in 1984
Q5. Inzamam-ul-Haq with 83 ODI fifties. Yousuf currently has 62
Q6. Saleem Elahi 102* v SLA at Gujranwala 1995 (with help from cricinfo :))
Cricinfo - Records - One-Day Internationals - Most runs in debut match