Executor dead for a will

an unregistered will is also valid and acceptable in courts. even a registered will can be challenged.

 Registration of Will is an optional.  A will executed by a person shall be attested by two witnesses with scribe (if the executor is a scribe not problem). It is must.  and a last will wether it is registred or not will come into operation only after the death of the testator

yes it is right 

a white paper and the person who is writing the details should be in sound mind and he should clearly mention to whom he is executing the property the name and if relation clearly and with two witness in each page

if in his life time if he want to change any item then a codicil document for change also on white paper should be made attached to original 

if the will is not registered is can be challenged iin any court only hand write will be questioned and the witness evidence will be taken in to confidence 

yes,according to Indian Succession Act will is valid and registration thereof is not compulsory.According to Registration Act 1908.