Unfortunately, the control panel doesn’t support installing the required files to fix this issue (the CA Chain). You may see this issue regardless of the SSL vendor being used.
This is not a PHP.ini setting, this is PHP code. You can just add this to your own website code, this is not something you can put in a configuration file.
Also, I would recommend to only use the line:
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
The other line should not be necessary (it checks if the domain in the SSL certificate matches, which should always be true).
You should not do this. Our servers do not support SSL v3 because it’s very old and very unsafe.
And just because the SSL certificate cannot be verified doesn’t mean all SSL settings should be set to the most unsafe values.
Not really. It depends on how your website was coded. But since you haven’t shared as much as a URL to the website, let alone important details as to where you see this error, what software you are using, or what REST API you are talking about, it’s impossible for me to say.