Are we only aloud to wear the Tzitzit Katan only at day time or also at night, can we sleep with it, can we also enter the bathroom with it. Thanks.
It is permitted to sleep with the tzitzis (Rema, Orach Chaim 21:3), and some do so based on kabbalistic sources, but this causes a question over whether a new blessing should be recited in the morning over the tzitzis. If one recites a blessing over a tallis gadol, or if one changes tzitzis in the morning, this would not be a problem (see Mishnah Berurah 8:42; Shulchan Aruch Harav 8:27). However, one should not have a separate tzitzis garment for sleeping in.
It is also permitted to enter the bathroom with a tallis katan. Although Taz (21:3) is stringent when the strings are revealed, it is not customary to be stringent concerning this matter (Peri Megadim).