Conditions for the validity of Salaah

Q: What would be an approximate time that one has to read Asr Salaah from the time Asr sets in until the makrooh time. 

Q:

1. If I start a Salaat at the time of sunrise, zawaal or sunset and then realise the time, must I break the Salaat or finish it?

2. If it's the time of after Asr or after Tahajjud, must I break the Salaat or carry on?

3. Is it the same for fard and Sunnat and nafl Salaat in the two answers for above questions?

Q: Is pre-coital fluid considered najaasate ghaleeza or khafeefah?

Will it invalidate salaah?

Q:

1. Is it necessary for a lady to have her hair covered while sleeping, cooking and when in bed making zikr?

2. Can a lady read salaat with jeans?

Q: I have a habit of making intention for Salat-ut-Tawbah, Shukr, Haajat & Tahajjud in a single two rakaat nafl salaah. Is this permissible and will it be more effective to do them individually?

Q: I was the imam in a salaah while travelling, a few other travellers also stopped, joined us and we performed salaah.

We had departed after Fajr, and had decided we will stop for Zohr at this location. After stopping we had meals etc. made wudhu and went to perform salaah.

At the time of starting the 2 rakaat jamaat salaah, I don't remember having a definite intention of performing Zohr Salah itself, although it was for this very reason we stopped. After saying the takbir the thought came into my mind that what salah am I performing? Is it Asr? Then I immediately realised no its Zohr.

After salaah I mentioned this to an alim there who said its fine, since we stopped for that very reason so "ilm" was evident, and "amal" as well was evident. When these two are found then this is sufficient, its not necessary to make the specific intention before salah.

1. Is this correct? Is the salah valid?

2. If it is invalid, what should one do when the musallis behind one cannot be traced?

Q: When determining qiblah direction, would a Google earth search be considered a valid qiblah direction?

Q: A person entered the musjid while the congregational salaah had started and he had not performed Tahiyyatul Musjid. Can he join the congregational salaah and intend (i.e. if it was Maghrib time) that he is performing 3 rakaats of the fardh salaah of Maghrib and he is also performing Tahiyyatul Musjid?

Q: I normally refer to the sunrise timing from the salah timings in Dubai which I Google. However sometimes there are differences of sunrise timings when compared with calendars. Some say 6:19, some state 6:17, some say 6:15.

So if I finished my Fajr Salah at 6:17am, which exact time should I use. I get confused which table should I refer to.

Q: Is a woman allowed to perform salaah with her niqaab covering her face in the presence of non-mahram men?