I'm running a production server with CentOS 7 and PHP 7.1. I'd LOVE to upgrade to PHP 7.4 but I am nervous about doing this on a production server. I am not the greatest sysadmin in the world, so I have a 3 questions, apologies if they are dumb/obvious to others :-)

1. I have to upgrade all my PHP extensions (like openssl, pdo\_mysql, iconv, json, gd, phar, pdo, libmagic, and a zillion others) at the same time, right? I can't use the existing extensions? So does this mean that I need to make a list of all those extensions, and then source the 7.4 versions to be sure I can upgrade all of them at the same time I upgrade the core PHP files? (Or is there some automated way to upgrade PHP and all existing extensions? Doing it "by hand" feels like a lot of work, and a lot of potential to screw up something. I'm just wondering if there's a more elegant solution that I'm overlooking.)
2. This is all on a production server (where PHP 7.1 runs as php-fpm under nginx). AFAIK the only option I have for upgrading is to take my site offline for maintenance, and then try to do the upgrade and hope nothing goes terribly wrong. Is that right? If so, how can I minimize the impact? I'd much prefer to get PHP 7.4 running perfectly alongside the existing 7.1 and then flip over to 7.4 on one quick switch, but can't figure out how. (EDIT: I should add that I am not using Docker or any other kind of virtualization. When I do `whereis php` I get: `php: /usr/bin/php /usr/lib64/php /etc/php.d /etc/php.ini /usr/share/php /usr/share/man/man1/php.1.gz`)
3. And then the best way to upgrade is... to use pre-built images that someone offers, like [Remi's RPM Repo](https://blog.remirepo.net/post/2019/11/28/PHP-version-7.4.0-is-released)?

Thanks.