Method of Salaah

Q: I heard that the Surah recited after Surah Faatihah in the second rakaat should be shorter than the one recited in the first rakaat. What is the Shar'ee ruling regarding this?

Q:

1. Must the surah recited in the second rakaat be shorter than the surah recited in the first rakaat?

2. If so, how is the length of a surah determined?

Q: Is it permissible to make dua in congregation after fardh salaah? Is there any hadith in which it has been called an innovation in Islam? 

Q: I read in tafseer Ibn kathir that Surah Fateha has seven verses in it and there are some Hadith also there in that tafseer from two sahihs that Bismillahir rahman nir Raheem is a first verse of Surah Fateha. There are only seven verses in Surah Fateha. Now, I saw in Sahih Bukhari Narrated From Anas bin Malik (radhiyallahu anhu): Nabi (sallallahu alaihi wasallam), Abu Bakr (radhiyallahu anhu) and 'Umar (radhiyallahu anhu) used to start the prayer with "Alhamdulillahi rabbil aala min" Vol-1,book 12, number 710. ( Sahih Bukhari-- characteristics of prayer). Now, what should we start the prayer with?

Q: Please can you tell me if my salah is valid if I forgot to say takbeer after the first tashahud and did not perform sajdah sahw.

Q: While reading salah, is it necessary to read thana at the beginning of salaah?

Q: What are the waajibat of salaah as per the Hanafi mazhab?

Q: Some time ago, I did not know that I have to read salah with tajweed. So for like almost 5 years I read salah but did not follow the proper rules of elongation and madds. Do I have to repeat the salahs?

Q: If a wajib is left out in Fardh salah, Witr Wajib salah like dua e Qunoot or sunnat and nafl salah, is it compulsory to repeat the salah after the salah time has expired?

Q: Can we recite sana when joining the Salah while the imaam is reciting a Surah?