What should a worshiper who has forgotten a pillar of prayer do?
If he/she remembered the forgotten pillar before offering it in the following Rakah (unit of prayer), then he/she should offer it, and continue the prayer, then offer Sujood As-Sahw (Prostration of forgetfulness) at the end of it. But, if he/she remembered that forgotten pillar after having offered it in the following Rakah, then he/she should offer a new Rakah in its (the one in which he forgot a pillar) place, and offer Sujood As-Sahw.
Is Hyena's Meat Permissible or Impermissible?
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
There is disagreement amongst the jurists as regards the ruling on eating hyena`s meat. Shafi`i and Hanabli jurists are of the view that eating hyena`s meat is permissible. The proof is the Hadith related by Al-Baihaqhi on the authority of Ibn Abi Ammar who said: "I asked Jabir bin Abdulla about hyenas, and he told me to eat them. I said: "Is it not game? He said: 'Yes' I said: 'Did you hear that from the Messenger of Allah?" He said: "Yes." And Allah The Almighty Knows Best.
Does wiping over one's socks during ablution permissible?
If the socks were thick, then wiping over them during ablution is permissible so long as wiping conditions are observed. And Allah Knows Best.
Is permissible to buy/sell with non-Muslim?
Yes buying/selling for a Muslim with non-Muslim is permissible as regards what is lawful.