We can break down the two opinions of how rav shimon bar yochai described how one can read krias shemah 2 times in a given period and be yoseh his yedey chovah for day and night- if we wanted to simplify the chiluk between the two versions- its taluy on how we classify the time period between alos and netz- whereas netz ledivrey hakol is yom, and lifney alos lidivrey hakol is layla- but according to the first lashon, alos to netz is considered uvkumecha (to a certain extent0 and in the 2nd extent its considered (uvshochbecha). Now, can we not bring a proof from daf bais amud bais where we said "siman ledavar tzais hakochavim"- where we had a raaya from the navi that the day was classified as starting at alos until tzais hakochavim- and thereby proving the first lashon in rav shimon bar yochai calling uvkumecha at alos the correct lashon ?
Dovid Kassin, brooklyn, ny
From Tosfos DH 'Lo' and (9a) DH 'Le'olam', it emerges that the Sugya which you are discussing is not concerned about when whether day begins at Alos or at Hanetz, but whether the period in between is considered night or day, a. with regard to K'ri'as Sh'ma and b. with regard to other Mitzvos. This is respective of whether day begins with Amud ha'Shachar or Tzeis-ha'Kochavim.
R. Eliezer Chrysler
There are two problems. (a) When is it day or night (b) Beshochbecho uvekumecha. Around this issue the sugya here and in pg 2a revolves. There is the baal hamoor who finds teh 2 leshonot are in contradiction and the all others disagree.
Also, can you say both in the same time frame? Now you cannot be going to sleep and getting up at teh same time. But, others can be in one state while you are in another.
Also, on Pg. 2a many acharonim (see R. Kaminetsky's sefer for example) are mechadesh that the Rashi is talking "ben hashemoshos". Hence, it is a sofek layloh (he is not interested in uveshochbecho mamosh) and tefilah lekulah while keriyas shemah lechumrah and must be repeated. the meforshim on Yureshalmi ask on shmuel who says sofek kriat shema is sofek derbanan from that memrah. They answer that it is deoraysoh only if he did not learn anything else. Shmuel is talking when a person learned something else.
Dovid Kassin, brooklyn, ny
Please re-write the questions without the Rishonim and Acharonim that you quote. There are far too many details for me to make out what you are asking.
Also in your introductory paragraph you write 'This is respective of whether day begins with Amud ha'Shachar or Tzeis-ha'Kochavim'.
I assume that what you meant to write was 'This is irrespective of whether day begins with Amud ha'Shachar or Haneitz ha'Chamah'. If you did, then the statement is incorrect, in that you wrote it with regard to both Keri'as Sh'ma and other Mitzvos, whereas Tosfos explicitly writes that as far as other Mitzvos is concerned, Amud ha'Shachar is still considered night.
be'Virchas Kol Tuv