In Shariah, there is no valid reason to accept Bitcoin or other Cryptocurrencies as a currency. It is just an imaginary number, which is generated through a complex mathematical process. It is purchased for Gambling or Speculations, and used in illegal or unlawful transactions”.
You said bitcoin is not halal but all the reasons you give I don't really support them bitcoin is haram because it is used for gambling so definitely our number fiat currency is also haram because lots of people also gamble with our normal currency so that's not a reason to give that bitcoin is haram, you said bitcoin is used for unlawful or illegal transact that those not make bitcoin illegal because our normal fiat is also use for illegal and unlawful transactions. I believe before you can say bitcoin is illegal you have to look for concrete reason and evidence that bitcoin is haram not the once you just gave.