#1
1) go went gone 2) lose lost lost 3) read read read 4) fly flew flown
5) understand understood understood 6) give gave given 7) begin began begun 8) forget forgot forgotten
#2
1) past simple 2) past simple 3) present perfect 4) present perfect 5) past simple
#3
1) play 2) know 3) played 4) knew 5) known 6) left 7) leave 8) left
#4
1) I have already finished reading this book.
2) We haven't had dinner yet.
3) Have they built a house yet?
4) He has never left London.
5) I met my friend last Monday.