No, not every creator can edit another creator’s knowledge article in BMC Helix.
Editing rights depend on roles:
Knowledge Users → read-only.
Contributors → can draft or suggest changes.
Publishers/Admins → validate and approve edits.

It is a common approach, indeed, only a few differences are present in the metadata presented. Articles created in both environments will be present in SyRA, if they have been set as visible to external audiences

In order to ensure the articles remain relevant and up to date, we have established guidelines for article reviews depending on the type and criticity of the article, as well as the weekly SO / Knowledge contributors comittee to review articles. 
Also:
- A notification is received by the article owner once the article is flagged
- We highly recommend that the reviews are performed promptly so that the article remains effective. 
For further details and guidelines, please refer to the "Knowledge KPIs and Governance" documentation available in the wiki platfrom

If the topic is relevant across multiple countries, you can:
-Select the “Syensqo” visibility group so the article is accessible globally.
-Or assign it to several specific visibility groups (e.g., different Proximity groups) so colleagues in those countries can access it.

SyRA is able to read the user's information and identify which country they are from. However, the KBAs are not classified by country, so it won't impact the visibility of the knowledge.

Either it is done proactively by nominating the replacing and communicate the new owner (through an IT request) or it will be checked afterwards and we will have to chase the team to find the right person and update the articles

The KBA approver is the Subject Matter Expert (typically the Service Owner), as well as users with Knowledge Submitter or Knowledge Admin permissions.
Once an article is created in Draft, it is assigned to the approver, who reviews and validates it before publishing.