Salaah

Q: If any Imam chews tobacco (zarda plan), is my salat complete behind that Imam?

Q: I made the intention in my heart to recite long surahs in fajr salaah, but I forgot and recited short surahs instead. Does this make sejdah sahw waajib?

Q:

1. Can one read multiple duas that come from the hadith after tashahud and before tasleem?

2. Can one read one dua multiple times after tashahud and before tasleem like: Bismillahi ala dini wa nafsi wa waladi wa ahli wa mali Or Allah humu ini aoothbika minal mathami wal magram?

Q: I would like to know if I read Fajr Salaah and after I finished, I saw the time was 5:39. Few seconds later, when I checked the time again It was 5:40 and sunrise is at 5:40. Should I repeat the salaah or is it okay and within the time?

Q: While lying in bed I am sometimes unable to face the Qibla as I need assistance and it is difficult for my wife to do it alone. Should I still raise my head or can I read salaah lying flat down (by raising my head I will not be face to Qibla still)?

Q: I was confused when exactly should one say "Rabbanna wa lakal hamd". Is it when you rise from bowing immediately or after you put your hands down and stand for a short while before going down? 

Q: I prayed asr with an imam. When I was in sujood, the row was tight and my elbows were touching my knees. If I remember correctly, I heard somewhere that you should not let the elbows touch your knees but rather spread them out. But is it essential for prayer to be valid?

Q: Can we offer Qiyaamul Layl while holding the Quran and looking inside and reading?

Q: I reside in an area and noticed that both mussallees and trustees of the local masjid are unmindful of zawaal, this is mainly on a Juma as we come early for jumah.

I find that people are performing nafl salaah during this time including the trustees and Ulema. The other masjids that I attend during this time either put on a light or a sign that say zawal.

I would like to know the following:

Firstly when is zawaal and how long does it last for? Example the times I see on the calendar for today as well as salaah times from crescent mobile says zawal 11:59am.

Does this mean zawal sets in at this time or ends at this time?

During this time of zawal what should be done and what should not be done?

Should I bring this to the attention of the trustees and will I be accountable For this if I don't?

This has been going on for the past 3 years or so. I dont want people to be offended and neither do I want to commit any wrong actions, thus when attending this masjid I look at zawal time on my phone and as a precaution I commence my nafl salaah 10 mins after the stipulated zawal time.

Q: During salaah, I sometimes wear a shirt which has a low collar, so a bit of my upper chest (under the bone below the neck) neck gets visible. Is the salaah valid?

Also, how much portion of the chest should be covered by men during salaah?