No it is not jaiz in Islam to hide such things, infact one of the only times one has an obligation to inform about others if they are making decision in the dark
Since marriages are arranged in our culture people should be open about it. Most of the time the person it affects wife/hubby to be may be open minded to disclosure but parents are reluctant. this causes major drama/problems later on because truth does gets out.
^I don't know, Islamically honesty is appreciated.
indeed...you may hide it from humans but can't hide it from Allah. and remember one worldly lesson: "A lie always catches up with you" OR "you can't hide a lie for too long, it eventually comes out".
1- Yes. There is a field 'declaring' a person was previously married, divorced or widowed.
2- Jaiz ya na-jaiz hony ki baat baad ki hy. Foremost a Muslim is ordered not to lie / A Muslim can't lie.