only missions you need to complete to unlock all achievements are as follows:


rescue olivia the orca
saving dolphins
Seal Rescue
for saving sea animals

Defeat Sheep Puncher
for the boss achievement

save our sheep
Save our sheep II
for saving 100 sheeps

*for collecting 100 sheep, you dont need to finish the mission for collected sheep to register so feel free not to feel too pressed to not die and complete a mission. but it is recommended to finish the mission and not quit in the middle because you need coins from mission completion for 20k gold coins achievement anyway.

replay save our sheep II (playing and finishing this mission twice successfully), and play save our sheep once to get 100 sheeps total

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20k gold coins:

coins achievement count total coins collected lifetime so feel free to spend them on cosmetics whenever you feel like.
you can also see lifetime collected on the shop screen.

dont bother picking up actual coins from the ground each level. completing quests and bounties are your main source of income

dont forget to pick up bounty quests from the dog before departing for the mission and turn in completed bounties after finishing missions every time.