It is forbidden to touch ones member while urinating. However, one can touch it to cover themselves while bathing in river, because the fright of drowning in the water will ensure one will not be aroused.

It is generally prohibited to cover ones bris millah, bc it looks like they are ashamed of their bris. But for modesty, one may, like when they are facing towards people.

It is recommended health wise to drink with eating, use bathroom before eating, open ones mouth while steaming, to rinse with cold water after bathing, and to drink hot water while bathing.

There’s an אנטיכי- either a stove with compartments, one for water and one for coals. Or it may be a pot with two layers- top for water, bottom for water. Either way, it is forbidden to drink hot water from it on Shabbos even if the coals were removed bc it the heat is retained so well.

In a kli rishon one can’t add cold water that would cook. One may add a lot of cold water at once that would only get warmed. Into a kli sheini one can add even a little cold water that will heat it.

There a prohibition on Shabbos of מצרף- of hardening metal. After metal is heated, if one adds a lot of cold water to the top of the kli the Metal can harden. It is a form Of מכה בפטיש.

Adding a lot cold water to a kli taken off the fire (and it’s hot water removed) if ones intention is to warm the cold water and not to harden the metal kli- this is a dispute of דבר שאינו מתכון. R Shimon allows it and r Yehuda does not.

מלאכה שאינה צריכה לגופה- doing a melocho not for its objective reason but alternative reason. Like putting out a wooden coal with fire so people don’t get hurt. This is a dispute between r Yehuda and r shimon. R Yehuda says chayav and r Sholom says patur. This issue is not the same issue as דבר שאינו מתכון, and in fact, Shmuel holds like r Shimon regarding דבר שאינו מתכון but like r Yehuda by מלאכה שאינה צריכה לגופה.

Extinguishing out hot metal on Shabbos is only drabanan and it may be done to make sure people don’t get hurt.