Rabbi Avrohom Baruch Zachariash teaches the halachas of COUNTING the OMER with the Mishnah Berurah (O.C. 489).
00:45 After finishing early Shabbos, can someone count the Omer for the “previous” day.
06:55 Can a person count the Omer at Early Maariv?
09:35 Saying Keriyas Shema between “Alos” and “Sunrise” for BOTH night and day.
12:45 Counting as an “Onan”
12:40 489:8
30:55 489:3 Be’er Halacha counting after early maariv.