A. “Petur” means that one is completely exempt from the army draft B. “Dichuy” means postponement, it's a term used to describe the status of a Yeshiva bochur enabling him to postpone the draft as long as he is enrolled in a Yeshiva
Yes, though this might not be necessary since there are ways of avoiding the draft while maintaining Israeli citizenship
Yes, as long as you don't have a status of “deserter/ עריק”
Yes, as long as he is enrolled in a Yeshiva he can maintain his Yeshiva Bochur status and is eligible for a draft deferment (if he already spent time learning in a yeshiva in Israel circumstances varrey)
No, only people who fall into a specific category of "Draftable"- generally this exempts Women, men over the age of 22 and Yeshiva Bochurim who will continue learning in Yeshiva