Are Sephardim allowed to shave/trim next Friday (the 31st day of the Omer) during the day?
According to the Rema and Ashkenazi custom, it is permitted to take a haircut or shave and trim one’s beard from the 33rd day of the Omer, and when this falls on Sunday it is permitted to shave etc. from Friday in honor of Shabbos.
However, according to Sephardi custom it is only permitted to take a haircut from the 34th day of the Omer, and when Lag Ba’Omer is on Sunday it is only permitted to do so from Monday – and not from Friday. Lag Ba’Omer falls on Friday, it is permitted to take a haircut on Lag Ba’Omer even for Sephardim (see comment).
The source for this is the Shulchan Aruch and Rema 493:2.