No, is the simple answer,if you don't win the the first time, it resets to the starting amount of troops.

I noticed that they changed what you have to do, for the competitions, but there's still the stupidest amount of kills needed for a piddling amount of reward,even for the first level, at least for me,that it's not worth the effort.

Thanks. I find now that attacking Paladins is only good for losing a certain number of troops so I can get the rewards when healing them again. 

I.e I am as far as I can go without levelling up (....which I guess is precisely what Plarium would like me to do in the hope that I then have to buy something?)

2nd question - is there any advantage to knocking out the scouts? As far as I could tell it made no difference to progressing to the next level.

 Much the same for me. 

The day they went live,I rushed them on one account,at first it was fun, then became tedious, so much so, I gave up with others.

I didn't claim the rewards,and when they changed them,the unclaimed ones changed too, so I lost out.

Par for the course with what they do with game, let the spenders get a super advantage and spoil it for the slow coaches.

Scouts, also currently no, once you know what's there, it stays the same,and follows a pattern,so now they know we know, watch for them changing that too. 

 ''I find now that attacking Paladins is only good for losing a certain number of troops so I can get the rewards when healing them again.''  

 As with much ,if not all of the game,I suspect that this is a net gain is an illusion, if not a delusion