I've just started studying derivatives from the "Options, futures, and other derivatives - J.C. Hull" and I'd like to see how to do hedging and trading transactions through a simulation platform or a demo account. What do you recommend me?
I don't know about the "best" but from personal experience:
Interactive Brokers: If you have a live account with IBr, they will give you a demo/paper trading account along side of it that you can use for testing purposes. I used it a long time ago. I don't remember if the simulated order fills were accurate but other than that it had the full functionality that a regular account would have including API access.
Lots of other brokers have demo/paper trading capabilities. I wouldn't recommend using them for much other than testing very basic things like API functionality, order entry/cancellation, system messaging, etc.
Hope this helps. It's not exactly on topic for this SE but I remember 25 years ago when I was looking for similar information as this and I am sympathetic. Good luck.