Here is a full walkthrough with all levels guide in Flying Soldiers.
Introduction
At times, you may be required to interact with objects (lockable door) or use an ability (roll).
Some levels require timing.
It is recommended to view the images closely for more detail.
Summer Campaign: Mission 1 – 15
Fall Campaign: Mission 16 – 30
Open lockable door after switch is activated
Open lockable door after spike trap is activated
Open lockable doors when the trap starts to move
Open lockable doors when it is safe to do so
Winter Campaign: Mission 31 – 45
Open lockable door just before spike comes up
Roll early to break the wall
Open lockable doors when the trap starts to move
Don’t roll while in front of the other bird
This will take 2 different setups
First: 2 Medals (Roll to get the second Medal)
Second: 3rd Medal
Roll to get the First Medal and break the walls
With the first bird, roll early to be in front, then use a well timed roll to jump the moveable platform
Roll ahead until you hit the door
Let other 2 birds pass by then open that door
Thanks to Na for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.