0. Save your project as a single file and share the capx instead of zipping up the project folder.
1. Put a 'platform: is on floor' condition alongside the 'on D pressed'.
2. You have to set the PlayerImages sprite 'mirrored' or 'not mirrored' depending on which way he's facing. Actually you're already doing that with walking but for some reason you set him 'not mirrored' when playing the hit animation.
3. Change 'D is down' to 'on D pressed'. And change 'on D released' to 'playerimages: on animation "hitforward" finished'.
4. Give the 'on animation finished' event a subevent: 'platform is moving -> set animation to "walk"' like you've done for 'on landed'.