Not at all. Greenfoot does not have a mobile version, so you had to run an emulator which I don’t think is gonna happen on an iPad. You‘ll only be able to run the scenarios from the website

The short answer is no. You can use github or even dropbox to work multiple people on the same project (the first is to be preferred). Maybe I didn't understand your question. What exactly would you want to achieve by programming online?

I assume you want to code, test and upload from your iPad. If these things only the coding part will work. There are apps to edit java files, but you ain’t be able to execute them and error checking won’t work because that app ain’t know the Greenfoot API. The only thing that I could think of is using Steam remote play. This allowes you to stream a game to your mobile device, with full control over keyboard and mouse, and you can actually also open any other app while steam is open, so you can basically use it as a remote control + streaming system for you pc. I only know that it works for windows though and it’s not really made for that and your pc will have to run all the time but it should work.

I am a teacher at an "IPad school". So I am forced to program with Greenfoot either with the help of the iPad or with the help of the Internet. As far as I know, both options do not currently exist and I am therefore looking for a solution.