The third (messed up) screenshot shows Word Online. This is a different program that works on the same files. It has different (fewer) features and can give results like this. It likely will look like that if you open it in Word Online as well. That classmate should open the document in the full desktop version of Word.
The others likely are explained in Word MVP Suzanne Barnhill's page: Why has my document changed when I open it on a different computer?
Because Word is a WYSIWYG application, it will always try to represent
on screen the result you will get if you print on the printer that is
currently selected. Unless you have changed the active printer in
Word, this will be the printer set as the Windows default.
Changing printer drivers will almost always change the layout at least
slightly and sometimes radically. ***
There are a number of ways to minimize the changes that can occur when
you change printers or drivers:
Don't use hard page breaks! Using hard page breaks (Ctrl+Enter)
just
makes matters worse. For example, suppose you have inserted a page
break at the end of every page. If the copy that fits on one page
using one printer then runs just one line over using a different one,
you’ll end up with alternate pages containing only a single line of
text and a page break, thereby doubling the length of the document.
Instead, use style and paragraph formatting to keep text together.
Judicious use of “Keep with next,” “Keep lines together,” and “Page
break before” formatting will keep important sections together. These
settings are found on the Line and Page Breaks tab of the Paragraph
dialog, accessed from the Format menu (or shortcut menu) in Word 2003
and earlier; in Word 2007 and above, use the “dialog launcher” arrow
in the bottom right corner of the Paragraph group on the Home or Page
Layout tab of the Ribbon or the Paragraph… entry on the shortcut
(right-click) menu.
There is also a Compatibility Option, “Use printer metrics to lay out
document,” that may make a difference. ***
In Word 2007 and
2010, go to Office Button | Word Options | Advanced, scroll to the
very bottom, and click on the + beside “Layout Options.” This option
is not available in Word 2013 and 2016.
(nor in Word 2019/365)
What works best to preserve the look of your document, however, is to
select the printer on which you will ultimately be printing the
document (even if it is not connected to the printer where you're
editing). Then you will know exactly where the page breaks will fall.
Of course, that won't help if you need to email the document to
others—but the other suggestions will.
If you are emailing the document to others and preserving the page
layout is critical, one solution is to email your document in Adobe
PDF format. ***
Word 2010 and above have PDF authoring built
in.
This article copyright © 2003, 2016 by Suzanne S. Barnhill
Also, be sure that the option to "Automatically update document styles" when opening is not checked in the Templates and Add-Ins Dialog. (Developer Tab > Document Template).
![screenshot of dialog box](https://cdn.statically.io/img/i.sstatic.net/lCnqF.png)
See: What happens when I send my document to someone else? Will Word mess up my formatting? by Word MVP Shauna Kelly.