This, you already answered your question in the bolded part above.

Bitcoin is decentralized and there's no need to back up any third parties such as to have insurance.  Our responsibility is to take care of our private key privately because I believed in the old saying. "Your key, Your cryptocurrency".  Speaking of vulnerabilities, that's the problem of having Bitcoin if they didn't know how this works.  Learn first how Bitcoin technology stuff works before they accept and hold for future purposes.

That's impossible and beware of such services that offer Bitcoin insurance.  I heard this so many times that there's a centralized service offer life insurance plan and they will hold your Bitcoin.