Some M1 Doubts?

When we are working out the magnitudes, in vector questions, and we are square rooting etc... do we need to show if there was a MINUS.

You know these types of questions whereby an object would be help up by a force on a plane....and then suddenly that force is being removed...wouldn't that object actually move downwards if that happens... But in this question from Jan 2012, http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202012%20-%20QP/6677_01_que_20120307.pdf
question no 8 part c), when the force holding it up is removed fascinatingly the object is still continuing to move up ??????????// How come this is occurring ? Is it a different case for all these different questions because I have always thought that if we removed the force, then the object would guranteed move down??????????


The also for this question from that same paper,

Question No. 4 part b? I did get the answer that they were looking for in the mark scheme , but then I spent quite a lot of time thinking that they actuallly required the MAGNITUDE and hence I went into resolving vertically etc .... without any success. Because I was all the time thinking that they required a number as the answer without any unknown in it?????????/ How do u know when u can give the answer as an answer with unknown in it ,, becuase it doesnt tell in the question always? Panicking me all the time. What to do?