This question pertains to how necessary it is to perform a bris on the 8th day from birth. I know that, if the baby is sick, it can be delayed (to a non Shabbat/Yom Tov day). This question relates to other reasons for delay, aside from health.
(1) Is it preferable, or even allowed, to perform a bris on the eight day after sunset (shkiah) but before nightfall (tzeit hakochavim), or should you wait until the next day (9th day, assume melacha is allowed) and perform the bris between sunrise and sunset?
(2) If 10 men aren’t able to be assembled for the 8th day, are you required to wait until a later date for a minyan or should the bris be performed on the 8th day without a minyan?