I've done all of them. Can you do them?
Actually, they are not very hard.
1. Complete It's Raining Seeds without remove any fog. (Difficulty: 7/10)
2. Complete Bobsled Bonanza without melt any ice trails. (Difficulty: 6/10)
3. Complete Last Stand without use any instant kills. (Difficulty: 8/10)
4. Use a normal Wall-nut to kill a Dancing Zombie before he summons Backup Dancers in Wall-nut Bowling 2. (Difficulty: 7.5/10, Lucky-based)
5. Complete Air Raid (hidden mini-game) without lose any Lawn Mowers and Pool Cleaners. (Difficulty: 8.5/10, Lucky-based)
6. Complete Dead Zeppelin without use any Bungee Zombies. (Difficulty: 7/10, Lucky-based)
7. Complete Me Smash! without use any Gargantuars. (Difficulty: 7.5/10)
8. Don't use instant kills to kill a Giga-gargantuar. (Difficulty: 9/10)
9. Collect all Zen Garden plants. (except Marigold) (Difficulty: 9/10)
10. Don't use instant kills, Gloom-shroom, Butter, Umbrella Leaf or Ice-shroom to kill a Bungee Zombie. (Difficulty: 9/10)