I want to divide this into three parts, as the answers are different:
See projects: Yes, enable anonymous "browse project" access to the project(s) you want the world to be able to see.
Create issues: In theory, yes, enable "create issue" as well as browse. But. You won't know who is raising the issues or have any easy way to get back to them with questions or updates, and it's an open invite to spam your systems. If you really need "anyone can raise something", consider using Jira Service Management instead, providing a request portal that anyone can sign up to, or have sensible "no account needed" access to.
Vote: No. The voting system in Jira is simple, and, like all proper democratic systems, has some simple protection against voter fraud - it records each vote by adding the user's ID to a list, not just a check mark. This stops anonymous voting as the first anonymous user who votes is recorded and then no-one else can vote again because "anonymous" already has voted. One person, one vote...
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