The first thing the Gemora learns from this story of Rav is:
That one may daven מעריב early/before sunset while it is still day. Just like Rav who davened Maariv early.
Is there a משנה in Maseches עדיות that rules like Rebi Yehuda regarding Tefillas Shacharis (that one can only daven for 4 hours)
Yes
Did R'Ami and R'Asi walk in front of someone who was davening?
Yes
The גמרא concludes since we find some רבנים who hold like Rebbi Yehuda and some רבנים who hold like the CHACHOMIM, there is no final פסק. Therefore...
You can choose when to daven maariv
R'Ami and R'Asi only passed in front of someone who was davening if they were...
4 amos away
The third thing the Gemora learns from this story of Rav is:
That you are not allowed to walk in front of someone who is davening Shemonai Esrai. Just like Rav who did not interrupt when he finished his Shemonai...
We learnt in the Mishna that there is a מחלוקת between Rebi Yehuda - רבי יהודה and the Chachomim - חכמים about when to daven Mincha - מנחה. What did R' Yehuda say?
You can daven Mincha until Plag Hamincha - פלג המנחה
Rav visited the house of Geniva. There, he davened the Teffilah of Maariv early during the last part of the day. His תלמיד, R'Yermiya did what?
Davened directly behind him
The second thing the Gemora learns from this story of Rav is:
That one may daven behind one's רבי. Just like R' Yirmiya who davened behind Rav who was his רבי
Is there a משנה in Maseches עדיות that talks about Tefillas Mincha?
No
From the story of rav and R'Yirmiya the Gemora learns how many things?
3
We learnt in the Mishna that there is a מחלוקת between Rebi Yehuda - רבי יהודה and the Chachomim - חכמים about when to daven Mincha - מנחה. What did the Chachomim say?
Until evening - ערב = the end of the day