I can't remember which friend working in IT told me forcefully years ago, 'The Cloud is just someone else's computer. Always have your own backups.' Following such advice from expert pals has invariably been a good idea.
I go with the philosophy that if you don't own the hardware where the data resides, you don't own the data. If I use any cloud-based storage, it's only as a backup of my backup.
time to back up my whole life on an external drive and then put it in a bank safe in case my house burns down
(I say this, not jokingly, but I know I probably won't do it because it's work)
Not just your own computer but offline storage for the important files.
When I was working on my Thesis, I not only had a disk at home (it was ca. 2000) but I kept one at work as well, so that if my apartment burned down I wouldn't lose everything.
Today, I have thumbdrives in a fireproof box.
Someone else's computer that is better run and secured than yours: source, people who have run and secured servers. When they say unprecedented, this one really is - but cloud is absolutely not a backup and you should have those too.
Yes. When I worked in house the decision was taken to move from internal servers to the cloud for cost reasons and no one ever explained to me what the recovery plan was if the cloud went down. It was just assumed it would never happen.