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1)

(a) If someone who wants his place of residence (over Shabbos) to be in the street, places his Eruv on a wall in the street, the Beraisa differentiates between whether he placed his Eruv above ten Tefachim or below.
Why must the Beraisa be speaking when the wall is at least four Amos distant from his chosen place of residence?

(b) Why is the Eruv effective when it is below ten Tefachim, but not when it is above?

(a) If he intends his place of residence to be a dove-cot or in a tower above ten Tefachim, and he places his Eruv above ten Tefachim (though not in his actual place of residence), the Eruv is effective, below ten Tefachim, it is not.
Considering that, either way, he is not permitted to take the Eruv to his place of residence, what is the difference between them?

(b) Why is it forbidden to move the Eruv from its location to his place of residence, even when both are above ten Tefachim?

(c) The Gemara asks that, according to Rebbi Yirmiyah, the Eruv should be valid, even if it was placed below ten Tefachim, because of 'Ho'il'.
How would 'Ho'il' work here?

(a) What does the Gemara mean when it answers that we are speaking here about ...

1. ... a Migdal Mesumar?
2. ... A Migdal Aruch?

(b) Why would the Din be more lenient if the Eruv was attached to a string, which one could pull up from the one shelf to the other via a skylight in the cupboard?

4)

(a) Our Mishnah validates an Eruv in a pit of any depth. There is no Chidush if the pit is situated in a Reshus ha'Yachid.
Two diverse Dinim will apply if the pit is situated in a Reshus ha'Rabim.
What are they?

(b) Since there is no Chidush in any of the above cases, in which case is our Mishnah speaking, and what is the Chidush?

(a) If someone placed his Eruv on top of a stake or a pole at whatever height, his Eruv is valid, provided they are not attached. Rav Chisda established this Mishnah like the Rabbanan of Rebbi.
Why is that?

(b) Ravina established the Mishnah even like Rebbi.
How is this possible?
Why would Rebbi agree here that the Chachamim decreed on a Sh'vus during Bein Hashemashos?

(a) What did Rav Nachman advise his Talmidim to do, when the town hosted numerous troops, and there was no room for them in the Beis-Hamedrash?

(b) How did he reconcile this with our Mishnah, which permits using reeds only if they have been detached and stuck into the ground, but not otherwise?

(c) How does the Gemara prove this distinction to be correct from two Beraisos which give diverse rulings regarding whether reeds and other types of bushes are considered Kil'ayim in a vine-yard or not?

(d) The Mishnah in Kil'ayim writes 'Ein Markivin Pigam (red-cabbage) al Gabei Kidah Levanah'.
How will this Mishnah categorize Kidah Levanah, and how will we reconcile this with the Beraisa which included Kidan (the equivalent of Kidah) in the list of vegetables which constitute Kil'ayim when planted in a vineyard?

(a) Our Mishnah validates an Eruv which is placed in a large cupboard whose key is lost.
Why does the Gemara initially consider this 'Hu be'Makom Echad, ve'Eruvo be'Makom Acher'?

(b) If it is, then how can the Mishnah validate the Eruv? Why must the author be Rebbi Meir?

(c) The Tana Kama of Rebbi Meir (in the Mishnah in Beitzah) permits taking from the hole, if some of the bricks caved in, but not to actually remove any bricks.
Who is the Tana Kama?

(d) Is our Mishnah concerned with Shabbos or with Yom-Tov, and why is that?

(a) What does Rebbi Eliezer (in our Mishnah) say about a brick tower (even if is made of loose bricks), when the key is lost?

(b) There is a third Tana (according to Rashi's first explanation), who quotes Rebbi Eliezer (or Rebbi Elazar), who differentiates between whether the key is lost in town or in the fields.
What does this Tana hold?

(c) Is it possible to reconcile Rebbi Eliezer with this last-mentioned Beraisa?

(d) What does the Tana Kama of this Beraisa hold?