I dont think there is any perfect way to buy bitcoin anonymously and safe
Decentralized exchanges (e.g. bisq, hodl hodl) is the perfect option to buy bitcoin anonymously and safe. You don't need require KYC or personal information (anonymous) and no third parties will hold your coins, you have full control about your coins (safe). But, DEX trading volume still low... so its not fast transaction as CEX.
It is against the rule to do real world trading. Those who illegally sell rsgps through other websites or forums bots 24/7 to earn those rsgps. They usually get banned within hours and any account that has traded with those bot accounts will receive a ban eventually (people even got banned after months!).
That seems like CEX, but you don't have to submit KYC and they can froze your funds (ban your account)