Sharing my experience as Ive kept many Sindh registered vehicles while based in Islamabad
Replies as per your questions
1,Upon a transfer yes it is optional for a new owner either to get transfer details on current book or get a new book by paying new book's additional cost
2,Yes all books have to be in the return file you can check every old book's serial number mentioned on the new book and yes a single missing book does affects resale and value
3,If page number 1 is missing AKA running paper it does not has any harm but if any other paper is missing than it is a matter of concern
4,As you are saying k file is citing book lost etc than better get it verified in detail via an agent