A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
I'm not sure Merge is what you're after but it's worth trying Girish's suggestion to see if it works for you.
You can also use Home | Slides | New Slide and choose Reuse Slides at the bottom of the gallery that appears to insert slides from other presentations into the current one. Or open both presentations, put both in slide sorter view, select/copy the slides from one and paste into the other presentation. You'll have the option of retaining the original presentation's formatting or applying the formatting from the presentation you're pasting into.
I'm not sure that'd preserve hyperlinks, but it would only take a few seconds to try it and find out.
If not, consider keeping the presentations separate and just linking from the main presentation to the subsidiary ones.
Protecting the presentation against changes is a trickier matter. Saving everything as PDF once it's all assembled and if need be, relinked, would likely be your best bet.