The most secure way to gain from having bitcoins, with no risk at all is to lend them on bitfinex.com.
Use the code 5l4wLVc4LW when making a new account for a 10% discount on all fees.
Do you have a guide on the lending process? The website is confusing with all the investing jargon.
It is impossible to not have any risk if you are lending.
You are paying 15% of your interest for insurance of the funds, so it's not imposible.
Your statement is not correct.
You are implying that you are purchasing insurance against the default of the borrower, but even this is not risk free, you are only mitigating the risk.
The borrower can't default. He can't take take your bitcoins or fiat and leave. He is just using it for margin trading and he will get his position close when he is aproaching the margin limit. The insurance is in case of a sudden spike or drop in the price and the platform could not react in time to close his position so it will cover the eventual loss.