Nathan Explosion

There's your issue right there - use PHP7.4.x, 8.0.x or 8.1.x

Define 'reset'...do you simply want to delete the content that is in the stream, as opposed to the stream itself?

$record->truncated(false, 100);

It would be more beneficial to turn off "Post before registering" instead, which allows guests to begin creating a post, and leave it sitting there ... which I believe then triggers that email out to them to remind them to finish off the submission.

Go to the support page in your ACP and you should see optional patches available to fix this.

In that case you'll likely have to use the cookie you mentioned (which expires after 3 months)
That gives you the user's ID, and you could then use the REST API to get more information about that user.

Go into your ACP, click the bell and I am pretty sure there is a notification setting for that.

They should click 'Notification Settings' and see what is set for the relevant item - if "No Notification List" then no notification...

In your acp, type display name into the search bar and click on 'allowed display name length'

Go here: https://invisioncommunity.com/clients/purchases/
Click the 'manage' button beside the item
Click 'Reactivate'

Give this a try - plugin instead of trying to write some javascript.
It will insert this:
<div class="popup" id="51f18_16504"></div> <script src="https://www.powr.io/powr.js?platform=html"> ...on every front-end page of your site, apart from the /login page.
(NE) Exclude _ hide script from loading in the login page 1.0.0.xml
Off to the pub now, back tomorrow.

All plugins are in applications\core\interface\ckeditor\ckeditor\plugins\ - custom ones are cunningly named custom-.......

{{if \IPS\Member::loggedIn()->inGroup(array(2, 3, 4,8, 10, 16, 19)) AND \in_array($item->container()->_id,array(3, 15, 23, 56, 73))}} STUFF {{endif}}  

OK, then Google is likely to be stopping you from logging in because it is considered to be insecure - they no longer allow the use of the "Less secure app access" setting to avoid this, they disabled it recently.
Do the following:
Login to the account in a browser Go to https://myaccount.google.com/u/3/security Go to the 'Signing in with Google' section and enable 2FA Once enabled, you will then have an entry titled 'App passwords' - click it Change the 'Select app' entry to 'Mail Change the 'Select device' entry to 'Other (custom name') Click 'Generate' Use that password in your IPS email configuration instead of the main account password    

Add this to your template:
{{\IPS\Output::i()->jsVars["variable"]=$value;}} Then use this in your JS code (assuming it is using the IPS framework):
alert(ips.getSetting('variable'));  

Have you enabled the "Can post HTML?" setting in your group membership, which will expose the 'Source' button in the Editor to allow you to view and add HTML?

Yes.

Contact the developer of the application.
 

Yep - you are shown only those items that are compatible with the version you running.

I'm not aware of one (if I was, I would have linked to it) - shouldn't be too difficult to code, either, if it's a per-app basis that you want it on.