بسم الله الرحمن الرحيم
(1) Only by standing beside the grave of a Prophet you may request him for dua.
(2) Whatever you have read ask Allah to send its reward to so and so person.
(3) Do not travel for it specially. However, if you visit a place sometime then visit the grave of elderly saints and read whatever you want and send its reward to them as mentioned above.
(4) No, it is not lawful to put flowers on the grave nor it is lawful to consider the flowers of that place sacred.
Allah knows Best!
Darul Uloom Deoband