Use calcium hypochlorite tablets for water purification?

Don’t try this at home based on what I say! I am just starting to learn things. I understand that whatever I do is at my own risk, and I don’t intend to do anything for a long time. I don’t pretend that I know a lot just because I am posting a long question with a few links in it.
“The internet” (https://www.backdoorsurvival.com/a-preppers-guide-to-bleach/) has told me that I may be able to use calcium hypochlorite powder for water purification. (If my math is right, then that article is telling me to do that at a ratio of about 0.8*10^(-5) to 1 by volume.)
So I have 5 questions:
1. Is this correct?
2. If yes to #1, what safety precautions should I take (other than being careful about storage and using proper protection and caution when mixing)? Are there some brands that are likely to be better than others?
3. If yes to #1, would it make sense to use crushed calcium hypochlorite tablets instead? (first one I found here: https://www.usabluebook.com/p-354074-usabluebook-calcium-hypochlorite-chlorination-tablets-45-lb-pail.aspx)
4. If yes to #1, what shelf life can I expect for properly-stored calcium hypochlorite powder, and what steps can I take to maximize shelf life?
5. If yes to #3, what shelf life can I expect for properly-stored calcium hypochlorite tablets, and what steps can I take to maximize shelf life?