I think one player can win on all the wagering contest but I do think that players wont wager that much with all coins to win more than 1 prize unless someone is a big whale with much coins on his wallet. In case you have the highest wagered amount in BTC and LTC, you should win both IMO.
This kind of code is usually one time use only, so it is first come first serve. Not quite sure about the amount but it can be vary, but I believe it is good enough no matter how much is the amount as it is free money
here are few:
8MTC-XF34-NZ8B-ON31-11R2
X3TY-0CUK-E0XU-MLTN-WHRI
7XXH-YX10-MV41-GQX-A1SO
KO4S-PF21-R83S-21YF-OMU2
O0HK-EQ3A-MKNG-A1B2-KBL5
FIP4-LEBU-VYEX-FXEL-CXE4
enjoy