Legal Capacity

No, in principle it can be reversed, upon request, if the court finds it to have been unjustified in the first place, or the conditions that warranted the declaration no longer exist.

Any adult whose legal capacity has not been taken away by court.

Yes, but only with court authorisation. Parents of a minor cannot represent him in such a transaction on their own initiative, without court approval.

That person's spouse or relative (parent, child, sibling, grandparent or grandchild), or the the State (the Attorney General, or  his representative).

If the will is made after the person's legal capacity has been taken away, then it cannot be valid at all, as he/she lacked the legal capacity to  make it.  If it was made prior to this, then, on the face of it, it is valid, and will have to pass the  normal test of validity when probate is applied for.

The court appoints a suitably qualified expert in the field of mental health to make a report  regarding the person's legal capacity. It also hears the actual person, or his representative. It will also hear the views of the state's representative, usually someone from the General Custodian's office.

After the age of 18, children become adults, and as such acquire legal capacity. Until then they lack legal capacity for many actions, under Israeli law. Up until then their parents, as their natural guardians, are responsible for acting on their behalf in most matters.