The Tabligh Jamaat says that first comes da'wat, then Ibaadat.

Answer

For a Muslim the first act is Ibaadat. Fardh, Waajib and Sunnatul Muakkadah cannot be delayed for da'wat. Da'wat is an act which blends into one's daily life, starting at home with naseehat to the wife and children. It is to be executed whenever one finds it opportune. Da'wat is not confined to tabligh jamaat activity. Allah Ta'ala has created us for His Ibaadat. All other Deeni activities are subservient and secondary to Ibaadat. The Tabligh Jamaat talks drivel and is lost in

gulu' (haraam bigotry).

actual 15 day destination. How should he perform Salaat?

A. If the other town is not at the Safar distance of 77 km or more, then this person will be a muqeem, not a musaafir. He has to perform Salaat if full. If the other town is at the Safar distance, then his initial 15 day niyyat is not valid. He will be a musaafir and has to perform Qasr Salaat (two raka'ts Fardh).