Can I use an iPad/Tablet/Laptop/Desktop to learn how to code?

Yes, yes you can. It is more difficult to use an iPad/Tablet versus a Laptop or Desktop but all will work. You can even use your phone. Though the smaller the device, the harder it is to learn but you can. All you need to do (at the very basic) is to read about coding and try writing it down on a piece of paper. Then when you have a chance to reach a computer, you can code that and test your code to see if it works and what happens. So, go for it!