Yes this is a thing and it’s been around for quite some time. If you’re trying to approximate TeX, you may also be interested in MathML.

I need to go lay down; I’m having flashbacks to the good old days of “XML everywhere for everything all the time”.

You don’t say what type of programming you do, or if you’re just learning or developing professionally, but maybe something fully online would work? For example repl.it, stackblitz, or Visual Studio Code for the Web.

I second the suggestion for getting a Bluetooth keyboard for the iPad.

It depends. I’ve done it a few different ways:

• YOLO: especially with thugs like PHP you only affect one page at a time and with low traffic the odds of a problem is small
• Maintenance page: temporarily show a page. Some servers like IIS have this built in. Otherwise it’s a simple update to httpd conf
• In a cluster environment, just take the node you’re updating out of rotation, and only update one node at a time.
• Copy and switch like you suggested. Can be combined with any of the above and is a smart move if upload is slow or can be interrupted, or it’s cumbersome to restore the old files

Edit: spelling

This is the answer. Here in this US checks are still widely used, and sometimes, thanks to processing fees, the only payment except cash someone will accept. Mobile payments, though available, haven’t really taken off here like in Europe.