Dua of Ka'b Ahbaar

Q: There was one sahabi who was a jew before, most probably Abdullah ibn Salaam or Kaab Ahbar (ra), who said if I did not read this particular dua, the jews would turn me into a donkey. Which dua is it?

Insect killers

Q: Is it permissible to use an electric/electronic device to kill off insects such as cockroaches, ants etc. Presumably such devices have a heating element under a plate and insects are literally roasted to death or simply electrocuted.

Salaah becoming qadha

Q: This morning I was going to wake for fajar and heard the namaz and saw someone else in the bathroom so I closed my eyes and waited. I didn't realise that I fell asleep and when I got back up it was still dark so I rushed to the bathroom to make wudhu. I am a very doubtful person so making wudhu takes some time but I am trying to get better and did it as fast as I could. When I came back I looked outside and it was still a dark blue and there was little  yellow in the far back so I quickly started praying. I didn't think it was that late as fajar happens around 6. I thought it might be 6:30 at the latest but after I prayed 2 sunnats I checked my phone and it was almost 7. So I finished my namaaz. I know it is bad to delay prayer and I didn't mean to. I am so worried I might have prayed in the forbidden time but I remember reading that if you didn't mean to delay fajar prayer you can pray as soon as you remember or wake up so did I do the wrong thing? How do I fix this?

Not experiencing haidh

Q: There is one girl. Her age is around 25. She is still not matured as she didn't get haidh yet. Is is because Allah Ta'ala's la'nat is on her because she consulted with many Doctors and hakeems but nothing happened. Please let me know what Allah Ta'ala says regarding this issue.