Extension of submission deadline –start of review phase at the same time?

We want to extend the deadline for the submission of new papers, but already start with the review phase as planned.
Is there a way to allow new submissions and somehow "freeze" papers that were submitted during the original submission phase so that reviewers can start reviewing?

Currently ConfTool does not offer a function to freeze already submitted papers and only allow new submissions, while also preventing authors to edit their already submitted papers. The reason is that this is often considered as unfair to the authors who kept the original deadline and now do not get the chance to improve their submissions further.

However, there are two things that you can do:

First, there is the option to inform reviewers automatically that a submission assigned to them has been updated by an author. To enable this function, please go to:
Overview => Settings => E-mail Settings
In the section "E-mail Settings for ConfTool Submission Functions" activate the option "Send BCC to Reviewers" (see image). This allows reviewers to consider also the updated version of the paper.

Second, you can create a new submission type for late submissions. Please go to:
Overview => Settings => Manage Submission Types / Conference Tracks
Copy the original submission type / track and all its settings by choosing the original track and clicking on the button "Copy as New Submissions Type / Track". Give this new submission type / track an appropriate name, e.g. "Full Paper - Late Submissions" and change the submission and reviewing deadlines accordingly.

You will find additional information regarding the setting of (alternative) deadlines when you go to this search page:
https://www.conftool.net/ctforum/index.php?action=search2&search=alternative+deadline&search_button=Search