Partial answer:
Do i have to register my Last will (Eg, Affidavit, Notary, Stamp, etc)
Does Last will requires any witness signature?
This is not legally necessary. One needs a written document signed by the person writing the will and by two witnesses (ideally with all three signing or initialing every page).
There are sometimes benefits to having an affidavit or acknowledgment before a notary around the time that the will is signed, but this is not legally required, and it is done less often in India than in many places. This is in part because the supply of notaries in India is extremely limited compared to most other common law and civil law countries. Only lawyers with many years of experience are allowed to be notaries in India, and India does not have a particularly large number of lawyers relative to its population.
The registration of the Will in India is optional. A will can be registered under the Indian Succession Act (1925) and the related Indian Registration Act (1908). If a will is registered, a probate proceeding can be dispensed with at the time of death. But the will can still be contested after the death of the person who wrote it, either on the grounds set forth below, or on the grounds that there is a subsequently executed document that revoked that will.
As a practical matter, if a registered will is indeed the last will that someone has signed, it is harder to contest a registered will than it is to contest an unregistered will, because most doubts about the formalities of the will and an initial judgment on the competence of the person writing it will have been made by a third-party government official at the time that the will is registered. Also, this makes it much harder to doubt the authenticity of a document purporting to be a will since it has been in the possession of a third-party government official often for many years prior to the death of the person who wrote it. Registering a will, rather than notarization, is the usual way to make implementation of a will proceed most smoothly at death in India.
- Can Last will over ride nomination? (Eg, Mutual fund, savings account, Stocks, insurance, etc) or i have to change the nomination of
each account manually?
Your nomination has priority over your will (unless the nomination is to "your estate"). Nominations are also sometimes called "non-probate transfers".
For example, if you will says "I leave my life insurance proceeds to my son", but the nomination with the life insurance company says "I leave my life insurance proceeds to my second wife" (since your first wife predeceased you), the life insurance proceeds go to your second wife and not to your son.
- How to divide my all assets & wealth in percentage (eg, dad 15%, mom
15%, Wife 15%, Child one 20%, Child two 20% and sister 15%). So, it
will apply to all of my assents like property, savings bank account,
stocks, etc
Your will will only applies to assets that are not governed by a non-probate transfer (i.e. asset that are not governed by a nomination). These assets are called your "probate estate". The amount of freedom you have to simply leave your assets to whomever you want in a will depends upon your family situation and your religion in India.
For example, a surviving spouse in a Muslim couple will have different inheritance rights than a surviving spouse in a Hindu couple.
Subject to legal limitations imposed by the applicable religion's family law rules, you can leave your assets to whomever you want. To the extent that no statute limits your options, the question of who you should leave your estate to is a non-legal question of personal choice. Drafting wills for people who have no descendants and never married and have no close living relatives is often interesting because there are often no easy default choices for what to do that are socially and culturally preferred, so you can get more creative.
I would not recommend trying to write this section of your will yourself. It is easy to write this part of a will in a way that seems clear at the time, but turns out to be confusing at the time that you die, especially if people mentioned in your will die before you, or assets mentioned in your will are not longer present at the time of your death.
Life does not always turn out as expected. Children die before parents sometimes. People who are healthy when a will is written end up dying before a person who had Stage 4 cancer at the time the will is written sometimes. I see these kinds of unexpected situations come up several times a year. Life is much less predictable than most people believe it to be.
Most people drafting a will themselves will write language which is reasonably clear if nothing changes between the time a will is written and when that person dies. But most people drafting a will themselves are not as clear as they could be about what happens if something assumed at the time that the will is written turns out not to be true at the time of death.
Once a will is written it remains valid and in effect until you die unless you change it, so you need to consider every possibility.
Competent professionals know how to write this language clearly. They also know how to talk you through different nuances of outcomes if particular people pass or if particular assets are no longer present in your estate at your death - often the professional will prompt you about what you would want (e.g. if your children predecease you and only your grandchildren are still living) raising issues that you never even considered could happen.
The will's language also needs to be clear about how debts and taxes are allocated.
Can my Last will be challenged in court?. If yes, then whom can
challenge my will (after death) and how long it can be challenged?
Yes. Your Last Will can be challenged in court, something that is called a "will contest".
A will can be challenged by anyone who would have received a better outcome if the will had not be signed, either because a prior will was more favorable, or because the outcome if there had been no will at all would have been more favorable. But it can only be challenged after you are dead.
To challenge a will someone must also assert a basis for doing so, such as that it is not witnesses, or a claim that you were not mentally sound, or that it was signed based upon fear, force, coercion, or undue influence.
Generally speaking a probate case can be commenced to give effect to a will after your death not less than seven days and not more than three years after your death. A will contest can be commenced up to twelve years after your death (and sometimes longer when there are extenuating circumstances).
But, as a practical matter, if someone waits too long to contest a will which has been admitted to probate and carried out, there may be no assets remaining to redistribute on the basis that the will was invalid, and no assets that can be clawed back from an heir who received that inheritance in good faith.
Also, the deadline for filing claims under the Inheritance (Provision for Family and Dependants) Act (1975), which provides for minimum inheritances for surviving spouses and minor children, is six months from the date of the Grant of Probate (if there is a will) or Grant of Letters of Administration (if there is not a will).