[SalesForce] Make an inputfield readonly depending on a controller boolean variable

The issue here is you are trying to rerender a section which was previously not rendered on the page. "Rerender" attributes only renders those sections or panels which were rendered on the page initially or before the ajax request.

So you would have to rerender the "Apex:pageBlock" or put your selectList inside an outputPanel like this:

<apex:pageBlockSection id="unlockFields" >
      <apex:outputPanel rendered="{!unlockFieldsVisibility}">
                            <apex:selectList value="{!newUnlockReason}" multiselect="false" size="1" id="unlockReasonPicklist">
                                <apex:selectOptions value="{!unlockReasons}" />
                            </apex:selectList>
                            <apex:inputTextarea value="{!newUnlockComment}" id="unlockComment"/>
       <apex:outputPanel>
 </apex:pageBlockSection>

If you want to avoid recursion the set of ids is the right way.

1. Before anything else, filter the chuck of records by their id and keep only the ones not present in the set or that do not have an id yet.
2. Update the set of ids.
3. Do anything you have to do in your before trigger.
4. If your trigger handles also inserts, update again the set of ids
5. Do anything you have to do in your after trigger.

Note also that:

• You can use a map if you want to enable the recursion of some records until a certain depth is reached.
• You can use multiple sets and maps to handle the recursion of different records in different ways.
• You can avoid to filter the chuck of records if it is a delete trigger to permit the deletion of the records even if it is updated/inserted in the same transaction.