1. Yes, Link will link the past registered users and their entry, when they next log into the site as long as the email addresses match in both the user account and in the entry.
2. Right now this is not possible. I’m nearing completing Link 2.0 which will enable front-end editing as long as Form 2.0 is installed and active. Form 2.0 is also under development and nearing completion.
I hope that answers your questions!