Tosfos answers that only blemishes that were present before an animal died are grounds for redemption, but that redemption can occur as long as the animal is still moving.
Rashi explains that the word is a borrowed term from wine inspection. The Gemora in Bava Basra refers to someone who smelled wine, and uses the same verb tahi . Similarly, Rashi explains that Rabbi Elozar was inspecting the statements, and delving into them, to understand them better.
The Shitah Mekubetzes, on the other hand, quotes an opinion that explains this word as a form of the more common matma - he was amazed.
Tosfos (76b v’halo zrika) states that Rabbi Elozar was challenging Rish Lakish, but only Rav Dimi’s version of Rabbi Yochanan’s answer – the case of the sacrifice whose blood was spilled before being splashed. Tosfos explains that their understanding of the Gemora in Chulin 80b is that the need for splashing blood can invalidate a slaughtering only if it was not ultimately done. Splashing of blood which was ultimately done will definitely make the slaughtering an edible one, retroactively.
Rashi, on the other hand, has a different text in the Gemora in Chulin, and therefore holds that even slaughtering a sacrifice which was successfully completed, including splashing the blood, does not render the slaughtering re’uyah since at the time of slaughtering, the animal was not edible.
See Pnei Yehoshua for a discussion of whether Rashi holds that Rabbi Elozar was also challenging Rav Dimi.
The halachah rules like the Chachamim. The Aruch Hashulchan infers from this topic a number of halachic conclusions. One of them is in the halachos of a shofar. The Gemora states that a shofar that is cracked is unfit. There is debate in the Rishonim on what extent of a crack invalidates a shofar, both for vertical and horizontal cracks. The Rosh (R”H 3:6) cites an opinion that any sized vertical crack (i.e., along the pathway of the air flow), no matter how small, invalidates the shofar, since the more it is blown, the larger the crack will become. The Aruch Hashulchan (O”H 586:15) states that this opinion does not invalidate it from the Torah, since we rule like the Chachamim. Rabbi Shimon can hold that a shofar that will become fully cracked is considered currently cracked, as part of his general opinion of kol ha’omed. The Chachamim, however, do not agree with this rule, and therefore would not consider the shofar already cracked. Since we do not rule like Rabbi Shimon, the invalidation must be on a Rabbinic level, lest we use a fully cracked shofar. [According to Tosfos’s limitation of Rabbi Shimon, it is debatable if Rabbi Shimon would apply kol ha’omed to a cracked shofar. There is no mitzvah of cracking the shofar, per se, but there is a mitzvah to blow in it, which would crack it further.]