Yes. Note, however, that there are issues with the size of PowerPoint files. They tend to contain additional information that is not required for display only and embedded graphics are often much larger than they need to be. In extreme cases your PowerPoint may be too large to upload to Moodle. Microsoft has some advice on reducing file sizes here: http://office.microsoft.com/en-us/powerpoint/HA011168821033.aspx
It is not possible to put text into Moodle without using a resourse or activity. You can, however, use labels from the resource dropdown to add text to the front page of your Moodle. Each topic box in a course also has an area or adding header text.
Yes. Beside each Topic Block in a Moodle course (and each individual resource or activity) you will see an eye icon (when your editing is turned on). If you click the eye so that it is closed, this entire block will be hidden from students on a course. Clicking the eye again will open it. This can not be done automatically, however.
1. Create two Grade categories, one for your activities still being graded, and one for your released activities.
2. Ensure that "Aggregate including subcategories" (an advanced option) is unchecked for your top level course grade category.
3. Edit the "unreleased" category's "course total" item.
4. Set the "grade type" to "none".
5. Tick the "Hidden" checkbox.
6. Save your changes.
7. Move all your activities being graded in the "unreleased" category.
8. Move all your activities already graded in the "released" category.
Generally, no. It is possible to set up a Moodle course to allow guest access, but this is rare and guests can not participate in activities. External users to Glasgow University Moodle courses and programmes can be given a manual ID account that authenticates their user information and details appropriately.