1) If I am writing a new page in Joomla, and add a link using Joomla Tiny MCE or JCE, will that normal link that I put in be later translated into a redirect link?
No, it will not automatically convert it to an iJoomla Redirect.
2) I already have articles in my site - will it create redirects for them automatically, or do I have to personally edit each and every one?
Yes, you will have to modify each one.
3) If a site user posts a link in a Fireboard thread, will Ijoomla redirect automatically notice it and change it to an Ijoomla redirect link?
Currently, there are not plans to integrate iJoomla:redirect into Fireboard at that level.