umm. is the blue block automatically jumping the grey block?
if the blue block has the platform beheviour. Then it has a lot of conditions pre built in. As in is(Moving/Jumping/Falling/Ground) on(Moving/Jump/Fall/Landed). It also has other criteria like unable to jump unless on the ground. So you are right the bluebox wont' jump without a Solid platform.
As for second situation. I have a hunch it stopped moving because your greybox is unable to make the Y condition of 500(hower that happens) before it moves left. So since grey != 500 then no move left :(
if you send your capx I/we can do more than just guess.