Are all inheritors entitled to a copy of the will? How is this obtained? Is the inheritor entitled to full disclosure of the assets and liabilities of the deceased as determined by the executor? What supporting document(s) are to accompany the inheritance check? Is there a repository where all of this information can be obtained?

U already knew the answers. All parties are entitled to docs re their
Part and probably to all parts.

Is this for a class or for a life situation?

I understand that, if there is no will in probate, one must have a Letter of Instruction to present to the investment establishment in order to collect the deceased's investment funds.
Please advise exactly what this letter must detail, who is to write/send it, and the express purpose of this requirement.
Thank you and best regards,
PC