Does the clipping of nails nullify ablution?
No, it does not, and it is preferable to wash the hands afterwards.
Is the marriage contract considered valid if concluded at home by the marriage official (Ma`zon)?
Yes, it is valid as long as it is registered at the court.
What is the ruling on someone who eats or drinks thinking that the night is still present, then realizes that dawn has broken?
Whoever eats or drinks thinking that the night is still present, then later discovers that dawn has broken, must refrain from eating and drinking for the rest of the day out of respect for the sacred month. However, they must make up that day after Ramadan, and there is no sin upon them.
What is the ruling on wiping over socks?
It is not permissible to wipe over most common socks today because the conditions for wiping are not met. The concession was reported for wiping over leather socks (khuff) and socks (jowrab) with conditions: They must be thick, not allowing poured water to penetrate, enable one to walk in them, be worn while in a state of purity (from ablution), cover the entire foot up to the ankles (meaning covering the protruding ankle bones), and not be torn. And Allah the Almighty knows best.