8 ways you have mentioned can really help you earn money but some of it are just very risky and can also lead to losing your money. In gambling, you can earn but everything there is a risk. Easy money also lose that fast. But if you want to earn bitcoin without investing your money, you can work for it. What you have to invest is your time and effort.
Gambling is very risky yes I know but not all the time gambling is not bad because they have good effect because you can earn more money in short period of time only. The other is less risk but takes time is really need to wait and your patient will be tested but they have some who are really good that gives you bitcoin in short period of time and that is signature campaign.