Are women obligated to daven Musaf?

As we have learned, many poskim hold that a woman is obligated to daven Shemoneh Esrei. This obligation only applies to Shacharis and Minchah. Ma’ariv, which was originally instituted as an option but has since been accepted as an obligation, was never imposed on women. There is disagreement about whether a woman is obligated to daven Musaf. Some say that she is exempt, since it is a time-bound mitzvah and is not focused on arousing mercy to fulfill our needs. 

סי' ק"ד ס"ה ס"ק י"ז ביאורים ומוספים דרשו 20

Is a person obligated to interrupt his learning in order to daven?

In the times of the Tanaim, there were people whose primary occupation was the study of Torah. Those people learned constantly and did not engage in earning a living (even for a moment). They stopped learning in order to fulfill most mitzvos, but they were exempt from the mitzvah of tefilla. Since tefilla is primarily a request for mercy, the requirement is not as stringent. As such, people in this category were not obligated to disturb their learning to daven. Nowadays, however, when there are no longer such people, one is obligated to daven even if he is in the middle of learning.  

ס"ב ס"ק ז' ביאורים ומוספים דרשו 24, 25

Does a magid shiur have to pause his shiur in order to daven?

A possible exception to the above-mentioned rule pertains to someone who teaches Torah to people who would disband (and not reconvene) if he would pause to daven and say Kriyas Shema. The following halachos apply to a person in this category:  1) L’chatchilah, if it is already time to say Kriyas Shema, he may not start a learning session if he is concerned that it will continue past the time for Shema. 2) If he began the shiur and it appears as if it will go past the zman, the poskim disagree about whether he is obligated to interrupt in order to say Kriyas Shema and daven. All agree that he should pause to say the first pasuk of Kriyas Shema and incorporate a halacha pertaining to yetzias Mitzrayim. 3) If there will be sufficient time to daven after the shiur is completed, he should not pause in order to daven. If he is learning with people at home and he started after it was already time to say Shema, some say that he should pause to recite the entire Shema.

ס"ב ס"ק ח'-י' ביה"ל ד"ה ואם

• One should not respond to Kaddish, Kedushah or Borchu during Shemoneh Esrei. Instead, he should remain silent and pay attention to what the chazan is saying. By listening to the chazan, it is as if he is saying the devar shebekedushah himself.

• The Rishonim disagree on the nature of the obligation to daven. Rambam holds that there is a Torah obligation to daven once daily. Ramban maintains that the obligation of tefilla is only mid’rabonon. Although this obligation is time-bound, Chazal did not distinguish between men and women in this case and they are both equally obligated to daven. Tefilla, which is a request for divine mercy, is crucial for everyone, regardless of gender. 

• Many Achronim rule according to the opinion of the Ramban. Therefore, women are obligated to daven Shemoneh Esrei. However, many women--especially those with young children--rely on the opinion of the Rambam and discharge their obligation by reciting just one tefilla.

• What should a person do if he is not sure whether he davened?

• What should one do if he is not sure whether he davened on Shabbos?

• What is a prerequisite for a tefillas nedavah?