One is not allowed to instruct a non jew to do melocho on Shabbos even to put out a fire. The rabbis were lenient by a fire and allow one to vaguely suggest to the non jew by saying “whoever puts out the fire will not lose.”

One doesn’t have to stop a non jew from putting out his fire. Even if it appears that the non jew is doing it for the jew, the reality is that The non jew is always doing it for himself, expecting some reward. In contrast, one must stop their child from putting out the fire bc the child is doing it for the parent.

One can use a bowl to cover a flame so it won’t spread fire, cover feces so children don’t touch it, and cover a scorpion so it won’t come to bite.

Children’s feces are not muktzeh bc dogs peck at them. Even though the feces wasn’t here when Shabbos began, since it’s likely to come, it’s not muktzeh. However, chicken feces are muktzeh and cannot be moved. The one exception is when they are גרף של רעי- in a place that’s disturbing humans by their repulsive smell and sight.

There dispute between r Yehuda and r shimon about מלאכה שאין צריכה לגופה. Acc to r Yehuda even if melocho is not done for objective sake of the melocho one is liable. But acc to r shimon one is exempt if they’re doing melocho for different reason. Trapping or killing animal is צריכה לגופה only to use the animal, so if one does it to protect themselves, it’s לא צריכה לגופה. Acc to r Yehuda it’s still biblically forbidden and acc to r shimon it’s only assur rabbincally.

If a poisonous animal is attacking a person, one can trap or kill the animal even acc to r Yehuda to save a persons life. Additionally, it may be permitted even if the animal is not attacking if one just steps on the animal in natural course of walking. However, to go out of ones way to kill poisonous animal that isn’t attacking is forbidden acc to r Yehuda. Acc to r shimon, one can even go out of their way to kill poisonous animals that aren’t currently attacking. Since it’s לא צריכה לגופה, the rabbis were lenient bc of potential danger. The gemara is not sure if this is only for 5 animals very prone to attack or to any potentially threatening animals.

If someone is able to kill snake that comes their way, they should know that HaShem gave them the merit to kill them. But if they don’t kill it, they should know they were only saved bc of a miracle.