1. Photoshop
A collection of Photoshop activities. They are in alphabetical order as opposed to levels of difficulty.
If you do not have access to Photoshop you can try using an online photo editor called Photopea. There is a tutorial you can follow as well. It may be glitchy in places. Keep in mind that it is not Photoshop and it is running within a browser so your computer may have compatibility issues or run out of RAM etc. Having said that, it is a really good way of practising a lot of transferrable skills.