The language available for FL Studio is mainly English, but the interface is also available in Spanish, German, French and Chinese. There is no mention of Italian being available as a supported language.
The full version of the software is confirmed by the product properties, which indicate a 'Full Version' with an unlimited time licence for one user. This means that the software includes all the functionality required for professional audio production without additional costs or time limitations.
The master is built-in with as many channels as you want. There are many possibilities to refine and change the assigned tones through the included master. There is an overview of the products you can buy on the Image Line website. From personal experience, the supplied masters are quite sufficient. I can also send you a screenshot so you can see what you can do. The YouTube channel of Image-Line also has many videos that can answer your question even more specifically.
LG
Yes, regardless of where you buy the licencekey, that's how it was for me too. The box only contains the serial key, which you add to your Image Line account. Updates can be downloaded/installed manually or automatically. Upgrading to a more expensive version or purchasing plug-ins and content is also possible at any time via the account.
there is no program that offers many plugins samples etc. like fl studio therefore fl studio also runs fluently (although it is the most complicated program i have ever had) but it is worth it try the demo version and think about it carefully