1)
When is "ba'Es ha'Hi"?
1.
Radak: It is like it says in Divrei ha'Yamim II, 36:10 "veli'Seshuvas ha'Shanah 1 Shalach ha'Melech."
1
Rashi, Radak and Targum Yonasan in Melachim I, 20:22 say that this is the end of the year. Metzudas David in Divrei ha'Yamim, Ramban (Bereishis 18:10) - some say that it is after one solar year, when the sun [and therefore shadows] return[s] to the same place as now. (PF)
2)
Why is it written Alah, and we pronounce it Alu?
1.
Radak: It is written Alah, for later he ascended and found them besieging the city. We pronounce it Alu, for his servants ascended initially.
