Nedarim 23 - 24 - A few points:

1. Regarding being oleh regel - the gemara seems to imply that there is a concept called "oleh regel" even post churban. The maharatz chiyus discusses this and suggests that people at least went to daven or perhaps even to bring korbanos. However, the Rosh says very beautifully that they came to study Torah "and even women were noheg a mitzvah to come there and see the kavod ha'torah". It must of been similar to the daf yomi siyum in MSG.

2. Kol Nidrei - The Rishonim seem to understand that the minhag of kol nidrei is sourced in this gemara (Tosafos) and the purpose cannot be for past nedarim for many reasons, rather the purpose is to make a stipulation on future nedarim of the upcoming year that they should be binding. Some Rishonim (Rabbeinu yacov Tam in Ran and Tosafos) recommends changing the text to clearly indicate that the purpose is for future nedarim. However, the Ran seems to hold based on the gemara that we don't want to publicize this concept that you can stipulate in advance to remove any future nedarim (provided that at the time of the neder you don't remember about it). Therefore, the text was specifically written with ambiguity as if it were referring to past nedarim, when in fact it is referring to future nedarim so that the amei ha'aretz would not realize that there is such a concept.

3. K'ilu Hiskabalti - The Ran says that this concept works only by an active condition to make it as if it were done, but does not work by a passive condition to make it as if it were not done. The Ran clearly indicates that this does not only work by a gift where it can be taken and returned, but also works for example if one would say something should be assur "if you do not go to a particular place", the madir can say that even if you did not go i accept it as if you went. But if one would say something should be assur "if you go to a particular place", the madir cannot say that even if you didn't go i consider it as if you went (the Ran brings others that permit even this case because it is all dependent on the will of the madir). What is really the difference? I understand by a gift that can be taken and returned, it makes sense to say "afukei matarasa lama li", but when the condition is not to receive something but rather an action that the mudar must make, how can we consider it as if he went when he actually did not go?

4. Ran on 14b indicates that there is no issur in neder shav (rosh argues). Ran on 24b indicates that there is no malkus but implies slightly that there is an issur. Ran on 25a says clearly again that there is no issur (at least in comparison to shavua).