InDesign document looks different when exported
Hello people,
I'm new to graphic design and I've been using Adobe InDesign for about 2 months. I'm currently voluntary working on a student magazine. I think I'm doing overall a good job, however I'm confused when it comes to techincal elements of importing/exporting a document(s). I want to do a good job and give those people that will print it (not on a home printer, i'm talking about those big factory printers that print magazines and newspapers) a correct pdf print version.
The problem I face is that my document inside InDesign looks slightly different than the one exported into "PDF (print)". I'll show with pictures what I mean:

Printscreen directly from InDesign while working (before exporting); I used multiply effect onto image btw.

Printscreen from Adobe Acrobat Pro XI Pro (this is view of exported InDesign document in "pdf (print)" version)

This is printscreen of the same exported pdf (print) document, just in another pdf viewer (SumatraPDF)

Printscreen how this vector image that i import into InDesign looks originally in Adobe Illustrator (printscreen directly from illustrator).
My ultimate questions are:
1) Is there any issue if I import picture in InDesign as a pdf file that is saved from Illustrator; does that couse any problems here?
2) Which one of these alternatives should I trust, or is there any way to really see how REAL print version will look like?
