Finally back from being lazy! (retrieved my lost password after a LONG while)
Click to reveal..

P.1 before P.5
P.2 before P.10, P.16
P.3 before P.4, P.7
P.4 before P.15
P.7 before P.11
P.8 before P.11, P.12, P.13

If I'm not wrong, I believe you also need to complete the first 15 puzzles before the flowers bloom for 16th one.