This refers to Moodle 3.11 from August 2022 onward
You can change dates, timing and number of allowed attempts for individual users or groups by following the links Group Overrides or User Overrides in Quiz administration. In situations where two group overrides may apply to a single user, the most lenient date is used.
Select the quiz in Moodle and then the cog icon to the right:
From the menu, select either Group overrides (if you already have groups you have set up for this purpose) or User overrides for individual students.
Depending on the option you selected, you will either be presented with a confirmation prompt to 'Add group override' or 'Add user override'.
You can then select the desired group from the dropdown, and change the other options as required, be sure to Save once finished.
For User override, the only difference is you select the correct student instead of group.
The following other resources are also relevant to this topic: