But then I believe that it is not 100% safe or not even the safest. It is still in the digital world wherein a lot are actually in the good go for bitcoin.
It's the safest, when you compare it against the top altcoins none of them came close to the level of Bitcoin. If you're looking to invest in Bitcoin short term wise that's where any investment gets risky.
2. Bitcoin is limited in supply , only 21 Million Bitcoin can ever be created. Out of which 4 million is already lost making it 17 Million.
What do you mean by 4 million already lost? Source? That's an overestimation I would say.
Could be an underestimation too since the article is almost a year old.
http://fortune.com/2017/11/25/lost-bitcoins/