3. What are the advantages of posting preprints? The main advantage of posting preprints is that your work will gain a lot of visibility very quickly. Preprints are open access, meaning that they are free and can be read for free by anyone, from your family members, to a member of a journal editorial board specifically tasked with searching preprint servers for interesting articles. Here are some great quotes from people who have posted preprints. Some of the most quoted advantages relate to visibility, collaboration, and a boost in job security.
4. What is PREreview? PREreview is a free online platform for collaborative writing of preprint reviews after discussion at scientific journal clubs. The website is supported by Authorea’s infrastructure, allowing reviewers to write and publish (with a free DOI, digital object identifier) their feedback directly on the PREreview site. The goal is to create a collaborative space for a community of preprint reviewers to grow and flourish in a supportive environment, perhaps lifting some from the pressures that might arise from posting feedback directly on a  preprint server. In addition, the platform hosts easy-to-use resources that will guide scientists on writing peer reviews, as well as ways to lead preprint journal clubs at their home institutions. To learn more about this initiative, visit PREreview.org and read a recent post on eLIFE Labs and the related ASAPbio Peer Review Commentary.
5. Can I/my student take down the preprint and submit to a journal? No, preprints are permanent versions of your scientific manuscript. They receive a DOI (digital object identifier) that makes them citable and time stamped as being posted on a particular date. However, you can post another preprint version after you have incorporated feedback from peers, and this will have a new DOI. Most preprint servers will display the latest version of the manuscript but will link to previous versions. For example, Figure 3 shows a screenshot from the bioRxiv website with the latest version of a preprint posted on December 1, 2017 (doi: https://doi.org/10.1101/171314).