Salaah

Q: I was always of the impression that the muqtadee should recite tahmeed in qaumah after the imaam completes reciting tasmee. However, I was lately informed by certain Ulama that the muqtadee should recite tahmeed at the same time that the imaam recites tasmee. I would like to know whether this is correct? I also wish to know whether all my past salaah are valid since I have always been reciting tahmeed in qaumah after the imaam completed reciting tasmee.

Q: Suppose I come to the masjid and I have little time before zuhr jamaat to pray the 4 sunnah muakkadah. Can I pray 2 unit rakah before fardh and 2 after fardh so that I can join the jamaat or the 4 units cannot be split?

Q: I follow Hanafi madhab. Since a few days, our Imam is praying dua in fardh of fajr salaah. On the very first occasion he did this dua in the fardh of fajr in the second rakah before going to ruku and from the next day he started doing it after getting up from ruku.

Now with the differnce in these 2 days, is our fardh salaah valid on both occassions? I know about the special prayers to make when in distress if the Islamic world is facing problems but is it allowed in the Hanafi madhab?

Q: In fard salaah, if a persons wudhu breaks infront of you, can the person behind him take his place by moving forward? What is the best option in this regard?

Q: Ishraaq is read 15 minutes after sunrise. How long after that is it permissible to still read ishraaq? 

Q: Can a person who is not regular with his farz namaaz be eligible to offer tahajjud namaaz?

Q: I can walk easily, can stand for a long time, but the problem is to bend my knees. So I can't make sajdah easily. My doctor advised me not to do salah by normal way? How do I perform my salah?

Q: It is written in Behishti Gohar that it is allowed to prevent a person from crossing in front of him while he is praying. However, if 'عمل کثیر' happens, then the prayer will become fasid.

What will be considered عمل کثیر ? What should the musalli do to prevent the person from crossing him?

Q: Regarding qadha salaah (missed prayers):

What is the full intention to make before one performs a qadha salaah (Note: the intention for ample salaah missed not just a single salaah). I am fearful that if my intention is incorrect my qadha salaah wont be accepted. Many books have the intention for only missing one prayer. 

To my knowledge the intention is "O Allah, I am reading the 1st fajr of those that I have missed" but I am unsure if it is correct.

Q:

1. Can a Hanafi perform asr salaah in the Shaafi asr time if leaving for a journey or while traveling?

2. If permissible, do I have to be traveling the safar distance?