Secret Meta Techniques

[3rdProspect]

I've put just under 100 hours into CW2, and I feel like I'm intimately familiar with all the mechanics and almost all of the strategies in this game, but there are thousands of cool looking custom levels that seem impossible, only beatable with hacks or mods. Are there techniques and exploits you won't ever learn from the Story/Bonus missions that everyone has figured out? How are you intended to complete missions with conditions that make levels unwinnable by normal means, like when objects are placed on TOP of ground, making it undiggable/inaccessible?