In order to make a siyum on a mesechta, does one have to leave over the last piece for the siyum, & if not, how soon after completing the masechta does one have to make the siyum?
I am a firstborn. Suppose I wake up late on Erev Pesach and walk into shul right after they finish the siyum. Can I still partake in the post-siyum meal, or am I too late? More precisely, what are ...