Diversification of investments is the answer to above questions, you cannot afford to trust any single product and invest all your earnings into it, as the future is unpredictable and doesn't guarantee you the success so investing in all products by dividing your earnings can give you more probability to earn profits.
Yes, diversified of investment objective is that we put the fund into some kind of asset
True or not, the answer is depending from where we see it
There are some investors who are pro or disagree with the statement that investment, because if we invest in one type of investment, when we lose then we will lose the total investment. This causes the value of our investment will decline pretty much
But there are also investors who do not agree with the counter or diversified. Investors this model usually has the ability to control their investments, have education, experience as well as excessive money. Like warren buffet?