The Gemara says one can recite Havdalah while it is still day (Shabbos). If Havdalah is meant as a separator between Shabbos and the weekdays, how can this be done while it is still day?
The Gemara relates how the student approached Rabban Gamliel to ask regarding Tefillas Arvis, and then proceeded to ask the same question of Rabbi Yehoshua. How is one allowed to approach another Rav with the same question already responded to by a previous Rav (see Avoda Zarah 7a)?
Regarding the second question, I have two thoughts:
First, the question was not in a goal to actually do or not to do something, rather learn, and maybe this manner does not forbidden.
Second, Rabban Gamliel was more senior than Rabbi Yehoshua (he was the president) so maybe in such scenario, it’s allowed.
Sounds very plausible, thanks for the comment
The Gemara in Avoda Zara is speaking about a scenario where the first rav gave a more stringent psask (ruling). In that instance it is forbidden to consult another rav to get a more lenient psak.
ת”ר הנשאל לחכם וטימא לא ישאל לחכם ויטהר, לחכם ואסר לא ישאל לחכם ויתיר
In our Gemara Rebbe Gamlel gave a more lenient ruling, so it was permissible to consult rebbe Yehoshua and accept a more stringent psak.