On a holiday (Yom Tov), are courtyard eruvin (eruvei chatzeirot) and techum eruvin (eruvei techumin) necessary?

When two facing balconies have a board connecting them, at what maximum length of board must they make a single joint eruv rather than two separate eruvin?

Eruv Placement Location

When two facing balconies are less than four tefachim apart (no board placed), must they make one joint eruv, or may they still opt for two separate eruvin?

Eruv Placement Location

When three courtyards open into one another and the middle placed its eruv in each outer courtyard separately (in two different houses), versus placing both outer courtyards' eruvin in one house in the middle courtyard — does this affect whether the outer courtyards are permitted with each other?

When Eruv Members Violate Shabbat

When two nested courtyards each made their own eruv (not joint), is the inner courtyard restricted by the outer's eruv problem and vice versa when the eruvin are fully valid?

When Eruv Members Violate Shabbat

When two courtyards with two intermediate houses each make separate eruvin, and each courtyard places its eruv in the house adjacent to the other courtyard, have valid eruvin been acquired?

Eruv for Connected Buildings

Is a city eruv required to encompass all alleys, or can individual alleys make separate eruvin independent of the city-wide eruv?

Eruv Techumin Food Requirements