None of them is necessary and the verbal declaration of the intention is not permissible as an obligatory precaution.
1- It is not permitted. 2- It is like the previous issue. 3- Yes, you can ask all religious lawful matters from Allah.
This person can perform qunūt after rukū‘ and then go for sajdah without rukū‘ and continue the prayer.
Perform the number of prayers that you are certain you have missed with the intention of obligatory qaḍā and if you want to perform more than that, perform them with the intention of precautionary qaḍā.
This act is makrūh (abominable) unless this is the only way of having presence of the heart (full concentration).
The distance between the last house of the departure city and the first house of the destination city should be considered as the distance for prayer to be shortened.
Your going out of your house to the work place and then going to sail from there until reaching the destination are all consider as one travel.
The Paternal homeland of a person is not considered as the homeland of that person unless he/she stays there continuously for a long time like one year.
Your prayers and fasting should be performed complete in both places.
It depends on the intention of the wife, if she hopes to convince her husband to return then it is not considered as abandoning the homeland and if there is no hope, then it is considered to be an inevitable abandonment.
If a person wants to stay 10 days or more in a place, in this case prayers should be performed complete and the person must fast. And if this person wants to stay less than 10 days then prayers should be performed shortened and the person cannot fast. The beginning of 10 days is from the moment of entering the destination, for example from noon of the first day of arrival until noon of the next day is considered as one day.
He should perform the qaḍā of prayers (i.e. perform them again later as compensation) that he has performed completely.