Looks like browser problem.
Here are some possible solutions:
Clean the browser by clearing all history from beginning
Reset the password of your first account
Login your first account with new password
Do not save credentials in browser
Follow the above steps for second account in different browser:
Open a different browser
Reset your second account ...
Form is the only way to reach out to Facebook. I have not seen any other way to contact Facebook.
You are not getting response because sometimes they take around months to reply. And sometimes they do not restore account at all if they notice policy violation.
From the link (Help Center) you have given in question:
Keep in mind that in some cases we may ...
None of the above work, including the "Facebook Analytics," which, for me, at least, works ONLY with my pages, but, I didn't care about that, so I didn't run it. My guess is that Facebook decided not to allow third-party apps to gain so much access to users' data for, hopefully, obvious reasons. You'd think they'd have realized that a lot of people want to ...
When I pressed "share" on desktop, I chose "write post", and there was no option I could see to include original post, just an emoji. However, when I did the same via mobile (Android), I could press the three dotted lines, and it brought up a context menu with "include original post" or "link only".
Not really. These sites do have an API, but they're more limited than the SQL access you get with SEDE. There may be third party tools that utilize the API to get more powerful data out of it, but which one of those comes closest to what you want to do is out of scope for this forum.
The APIs in question can be found here:
Just use the normal search box on top of the page. Write your keyword and press enter.
On the left side of the results page, you will see a filter box with the title: "POSTS FROM". In this section, click "Choose a Source" and write the page that you want to search inside.