Summit Brands Washer and Dishwasher Freshener Cleaner, 4 Tabs, 4-Count, Yellow, 4 Piece

Q: Is it safe and of good quality?

I am not a scientist, but it seems to be safe and certainly is of good quality. If you are concerned about safety, use vinegar.

Q: Can I use this in my Toilet?

I don't think it is recommended for the toilet and I would not use it in my toilet. Bleach and a toilet brush will clean and sanitize your toilet. BUT if you are trying to remove a hard water/mineral ring in the toilet, there are better options. A cleaning pumice will do the trick and it will not scratch the porcelain because porcelain is harder than pumice. Clean the toilet first, then use a plunger to remove some of the water (you don't have to remove it all), wear rubber gloves, then rub the pumice over the rings/stains. I have hard water and have to do it a few times a year.

Q: Would this clean the door boot seal gasket bellow on a washing machine?

I used mine on the dishwasher - I was not impressed. Didn't even do as well as just using a cup of vinegar. Try using a spray on kitchen/bathroom cleaner with bleach - that works on my washer gasket.