The text here: http://www.accesstoinsight.org/lib/auth ... gress.html
may be easier to read.
Mahasi Sayadaw's text is based on the Visuddhimagga, just describing what the stages are with reference to the Mahasi-style practise, which is described here: Practical Insight Meditation http://aimwell.org/Books/Mahasi/Practic ... tical.html
among other places. A more modern and complete translation is on this thread: http://dharmaoverground.org/web/guest/d ... age/443445
[it is listed as the fifth chapter of a longer book, but is the same thing]
You may find it useful to look at the summary in "CMA", A comprehensive manual of Abhidhamma http://books.google.com.au/books?id=hxo ... &q&f=false
You can read this on-line. The insight section starts on page 344.
zazang wrote:1. It says that the consciousness falls into Nibbana , where there are no formations. He becomes an Arahant.
After sometime , obviously the Arahant comes back to the sensual plane of existance. After this , can that Arahant again
and again still the formations whenever he wants or is it just a one time event in someone's lifespan ? Does the Arahant only see arising-passing of formations after that ?
Not necessarily an Arahant, the same process is said to occur for all four paths. It only lasts a few mind moments.
See CMA page 354, which discusses how the knowledge may be reviewed.
zazang wrote:2. After which knowledge attainments in this progress of Insight , does a person reach the 3 pre-Arahant stages ( Sotapanna , Sagdagamini and Anagamini) ?
The same process happens for all four paths.
zazang wrote:3. What exactly is the cause and effect that a yogi notices so that he starts believing that Paticccasamupada ( Dependent Origination ) is true ?
I'm not quite sure how to exactly map DO onto the Insight Knowledge, but I think that it is particularly the "Knoledge of rise and fall". there is some discussion in the Visuddhimagga XX 93 - 104 that discuss this.
zazang wrote:4. From what I make out , a yogi is supposed to note mental constructs and bodily sensations. What if both arise simutaneously ? Should he note any one of them randomly ?
I suggest you read Mahasi Sayadaw's instructions in the links I gave above and perhaps some of the links here: http://dhammawheel.com/viewtopic.php?f=17&t=341#p6695
. The usual advice is to note whatever is most prominent.
Hope this helps.