A few things on this one Kyuri..

A leg check is done by blocking your opponent's kick with your leg. Contract your knee and use the bent part of the leg as a shield. Its pretty easy once you try.

Your 'single' is actually what I call the double leg wrap. Thats a great replay and you should save it for the higher tiers. Instead go back and get another single leg replay it shouldnt be hard for you.

And the last one i would not consider a snap down, in fact it almost looks like a shovel, we don't do that here you should know better.
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After some reviewing the leg catch is okay just comeback with a new single and snap-down. Good luck.