There are different ways to approach this, but none of them is standard as the Contact Form 7 Integration plugin only throws data over the line and lets CiviCRM take care of the api.
First of all, it is well possible that standard Contact Form 7 lets you specify a box that prevents submission of the data? If that is the case then that is the quickest and ...
If the standard ACL's are not sufficient, you can add your own using hook_civicrm_aclWhereClause. Basically, you add more SQL "where" clauses to restrict which contacts are accessible. See the documentation for an example.
Seems like CiviCRM ACL might be your answer.
Native CiviCRM ACLs give more fine grained control, so, for example, you can limit access to view, edit, create, delete and search to :
groups of contacts
a profile (this is a collection of existing and/or custom fields, see "...
It looks like from your backtrace, its a bug in GDPR extension because its not possible to replicate in CiviCRM. Your system has many custom group for activity, and the extension code breaks when trying to retrieve results, Mysql supports max 61 joins in a query.
Disable custom group for activity which is not required.
Restructure your ...
Welcome to StackExchange. You can find many people who will do this on a paid basis at https://civicrm.org/partners-contributors
If you want to do it yourself and have specific questions then ask away on this site.
If you describe what your charity is, it may just resonate with someone willing to offer more substantial pro-bono help - but that's an ...
Yes at the moment the list is manually maintained (see https://github.com/civicrm/civicrm-core/blob/5.15.2/xml/templates/civicrm_country.tpl#L172). You can file an update request at https://lab.civicrm.org/dev/core/issues
The language of the question is a bit unclear, but I think what you want is a token that takes just the first letter of the first name. You don't need to collect it separately to do so.
If this is what you're looking for, please leave a comment to this answer saying so. I have an extension that adds a "middle initial" token, I could quickly adapt it for ...