For 3-21, not sure if its the right strategy but i have done 139870, i guess its close enough
With lots of trial and luck;
1st: middle of the left two pigs blow them both
2nd: on top of 3rd pig (left of highest stone tower) it blows the top 3 pigs, pieces pop the far right pig and stones, in the meanwhile breaks the bottom right column and debris fall on the bottom right pig,
3th: open space for the 4th bird, on top of the king pig, maybe you can blow him up but the score will ot be high
4th: blows up the king pig and the tnt.

Not much of a strategy is it