Using a western toilet

Q:

1. Is it allowed to use the western toilet in Islam?

2. While performing instinja on an indian toilet, water splashed on my feet and body from my private parts. Also sometimes, water splashes from the toilet surface. Are these splashes impure? 

Best durood to recite

Q: Does reciting Durood “Allahumma salli ala Sayyidina Muhammad wa’ala aali Sayyidina Muhammad wa baarik wa sallim” and “Wa sallallaahu alan Nabiyyil Ummiy” have the same virtues?

I have the intention of recting durood 1000 times a day. Which one is more beneficial?

Asking for forgiveness after doing wrong to someone

Q:

1. If a person wronged someone either at the age of 11 or under the age of 11 and didn't know the difference between right and wrong, will they be punished as they did not reach the age of puberty yet and sins are only accounted for once a person reaches puberty?

2. A person wronged someone and asked for their forgiveness and they forgave them. The wrongdoer doesn't remember whether they had asked forgiveness for the specific wrong they did or whether they asked in general, like forgiveness for any wrong or the wrong they did to then. They also repented to Allah and didn't do the wrong again. Is this enough?

3. If 2 people do a sin and the person didn't think they were doing wrong or harm to another person, does forgiveness need to be taken from the other person? The other person cannot be gotton into contact with. They have repented to Allah and have not done those sins again.

Hadith regarding a person who conceals his knowledge

Q: Can you explain who this refers to:

Rasulullah (sallallahu ‘alayhi wa sallam) said: “Whoever is asked about some knowledge (that he knows) and he conceals it, he will be bridled on the Day of Qiyamah with a bridle of fire.”

Imam Tirmidhi, Abu Dawud and Ibn Majah (rahimahumullah) have recorded this Hadith on the authority of Sayyiduna Abu Hurayrah (radiyallahu ‘anhu). (Sunan Tirmidhi, Hadith: 2649, Sunan Abi Dawud, Hadith: 3650, Sunan Ibn Majah, Hadith: 266) Imam Tirmidhi (rahimahullah) has declared the Hadith sound (hasan).