Re: Angels
Angels have no gender (are genderless). To reproduce is not dependent on having gender or being genderless. Allah making things to reproduce through pair of different genders is for material world only, as in this material world, we are tested, and for that all that happens around us has reason (Jawaz) created by Allah.
Else, all who gets created, their existence happens directly due to command of Allah, be they Angels, Jins, Humans or whatever. Whenever Allah wants to create anything he only desires and it get created. We do not know if Angels are fixed in number or not (nor it is necessary to assume that they are fixed in numbers). They keep getting created whenever Allah desires, or if they are fixed in number then also due to desire of Allah.
Name of Iblees is Iblees not Azazeel, though for some, Iblees is also known as Azazeel (probably influence of Jews and Christianity).
Iblees was not angel but was Jinn … [who happened to be amongst Angels due to his piety, and even though command of Allah to bow to Adam (AS) was for Angels, he also got included in the command, as being amongst Angels]:
Quran 18:50 … Behold! We said to the angels, “Bow down to Adam”: They bowed down except Iblis. He was one of the Jinns, and he broke the Command of his Lord. Will ye then take him and his progeny as protectors rather than Me? And they are enemies to you! Evil would be the exchange for the wrong-doers!
Reproduction through pairs is material phenomenon, not heavenly phenomenon. I gave you the answer to your question on reproduction, earlier.
There are 4 important angels (that Muslims are told). These 4 angels are:
Jabreel: He is angel of messages. He plays role of ‘communication mean’ between Allah and his prophets.
Israfeel: He would blow the trumpet that would destroy this created world and would start Judgment day.
Azraeel (Malakul-maut): He his angel of death.
Mikaeel: He is in charge of weather and good fortune for people.
As for Iblees (or Azazeel)… he was not angel but was Jinn … answer with reference from Quran is given earlier.
As for fallen angels (as you mentioned), they are not fallen, rather Allah sent them to this world on a mission (for a purpose), and that was to teach humans magic. Their names were Harut and Marut and they are mentioned in Quran.
Quran 2:102 … They followed what the evil ones gave out (falsely) against the power of Solomon: the blasphemers Were, not Solomon, but the evil ones, teaching men Magic, and such things as came down at babylon to the angels Harut and Marut. But neither of these taught anyone (Such things) without saying: “We are only for trial; so do not blaspheme.” They learned from them the means to sow discord between man and wife. But they could not thus harm anyone except by Allah’s permission. And they learned what harmed them, not what profited them. And they knew that the buyers of (magic) would have no share in the happiness of the Hereafter. And vile was the price for which they did sell their souls, if they but knew!