For completing the projects is Ubuntu required or it can be done in the windows
There is not any specific requirement that you need windows only or ubuntu only. It all depend on you. Windows operating system is generally found. Ubuntu is also good OS as it is totally virus free. If you still need ubuntu then you can install it as it is free. Or you can Dual boot windows and linux if you have good specs PC.
Ubuntu is not necessarily required for doing the projects mentioned in the training course. Windows is perfectly fine too. But if you have Ubuntu on your laptop/PC, it will be beneficial for you when you do projects related to Interfacing sensor over VPS. No need to create any account on the DigitalOcean for creating a private server. Just download all the required python libraries on your Ubuntu OS itself and proceed. But for Windows, you will have to do all of the above. This training explains well how to use both the tools. I used DigitalOcean inspite of having Ubuntu VirtualBox on my laptop just out of curiosity and I have no regrets so far. You can try them too.