If the eruv was lost, burned, became impure (as terumah), or rolled beyond four cubits — does timing (before or after nightfall) affect its validity, and how is doubt resolved?

After saying the blessing with rain mention 90 times (corresponding to 30 days × 3 prayers/day) on the first day of Pesach, what presumption applies if one later doubts whether rain was mentioned?

Rain Request (V'Ten Tal U'Matar)

If there is doubt whether water was used for labor, whether it has the required measure, or whether it is impure — is one considered clean, and must one use other water if available?

Who Must Wash Hands for Bread

When one washes twice (before eating, after relieving oneself), must the second washing (for Netilat Yadayim) be performed with a full revi'it, and how does the rubbing/scrubbing between pours relate to the validity of the washing?

Bread Cooked or Fried

If an obligated person's tzitzit are in doubt regarding their validity, must they still wear them and/or bless?

When to Don Tallit

May one recite a blessing (before or after eating) on a forbidden item?

Birkat HaMazon — Further Laws

If one is uncertain whether one recited a bracha (before or after eating/drinking), does one recite it again?

Doubtful Blessings