90% sure these are MOCs and not TLG designs.
S8302 - Is that Ghost Rider? JK!
S8303 - Shredder!? Wrong Ninjas theme. JK!
S8402 - Two minifigs included.
S8403 - Looks similar to S8402 honestly.
S8503 - Don't know where S8502 is though..
I'll let the pictures do the talking. I'll let you do the talking too below or through Facebook! Don't forget to like the page as well!