Is it an appropriate place to ask questions about language certifications like IELTS, CAE and others? E.g. questions about exam format, learning materials.
There has been some past discussions here on Meta. To list a few that I've found:
In sum, if your question is "What books should I use to better prepare for the exam?" then it is unfortunately off-topic on ELL. You can try asking in chat but I doubt many people active in chat now are familiar with IELTS or CAE (I don't know what CAE is). Your best bet is probably their official websites. Or you can see if there are dedicated discussion forums out there that might be helpful to you.
If you have a question from the exam that is about the English language, fire away. Be sure to include the exam-questions tag.
We do have a resource list where you might be able to find useful stuff.
For a complete review of English exams organised by Cambridge, visit their website and click on the tab, Exams and Tests. This will open a menu with a list of all their exams.
For IELTS, the site will explain the following:
•Total qualification time
Meanwhile, it's important to know that Cambridge decided to revamp a few of their exam formats in January 2020, so avoid English exam websites that are not up-to-date with the most recent developments.
The CAE has been renamed C1 Advanced. A candidate can find information about the following aspects
• Exam format (You can also download the four sample examination papers)
• Exam dates
How do I know about this? I am a qualified Cambridge Speaking examiner, it's my job to know :)