Hi,
To restrict the number of rows in an item list, start by establishing a form rule (refer to image -> 1-Form rule). In this process, I've employed a global constant to set the limit, comparing the item list count with this defined threshold. If a user attempts to add an 11th row, a confirm message will be triggered. Next, implement this rule in your item list through Advanced Configuration -> General -> Form rule invoked after callback (refer to image -> 2-Item list).).
To lock rows in an item list based on a checkbox value being true, specify the condition (not(checkbox value) or checkbox value = empty) in Column Edit Restrictions (navigate to your column in the item list -> Permissions -> Column Edit Restrictions).
Paste the same condition in the Column Edit Restrictions section for each respective column requiring this constraint.
Best regards,
Cristina