>Were the rules the same in Ireland when under English rule ? I need to fully understand
>it at the granular level and hence the many and detailed questions.
I think it is possible to spend a lifetime of study and not "fully" understand heraldry and its rules, much less how closely the rules are followed - or not - in practice.
In theory, yes, the rules in Ireland under English rule were the same as in England. In practice, however, it was primarily this way only in the areas under firm English control (e.g., Dublin). Out in the hinterland, English heraldic law was not so strictly followed.
>The coat of arms in Ireland was conferred to an individual not a family (Yes or No).
Yes.
>The individuals father and his grandfather were entitled to use the coat of arms(Yes or No)
Not unless it said so in the grant of arms. As one famous example, the arms that William Shakespeare bore were actually granted (posthumously) to his father John, though the application was made by William (who then, of course, inherited the arms).
>Were all the direct descendants of his grandfather allowed to use the same coat of arms
>(Yes or No)
Only if the arms were granted to the grandfather, and then only to direct male-line descendants.
>Were all the direct descendants of his grandfather allowed to use the same coat
>of arms (Yes or No)
Again, only if the grant was made (even posthumously) to the grandfather. And in that case, in theory, not the "same" arms. Only the eldest son (and his eldest son, and so on) ended up bearing the undifferenced arms. All of the other sons (and all of their sons) would bear the arms with a difference. In the English system of differencing, this usually involved adding a small charge - a crescent, a mullet, an annulet, etc. - to the arms.
That's the theory. In practice, the system of English differencing is cumbersome (imagine the fourth son of a fifth son of a second son, who would bear the basic arms with a small crescent charged with an annulet charged with a martlet; identification rapidly becomes an impossibility) and frequently ignored.
>Were only the direct descendants down from the individual to use the same coat
>of arms (Yes or No)
If the grant was made to him, yes, his male-line direct descendants would be able to use the same coat. Again, with the proviso that under English heraldic law, only the eldest son would inherit the undifferenced arms. The younger sons (and their male descendants) would be expected to (though often didn't) bear the arms with a difference.
>The individual's siblings were entitled to use his coat of arms (Yes or No)
No. If the grant was made to the individual, his brothers would have no entitlement to the arms.
>The individuals's siblings children, grandchildren were entitled to use his coat of
>arms (Yes or No)
No. If the grant was made to the individual, his nephews and his nephews' children, would have no entitlement to the arms.
I hope that all of this information is helpful to you. It's a complex field, and what occurs in practice does not always follow the prescriptions of the heralds. To borrow a line from the movie Pirates of the Caribbean, “The code is more what you’d call ‘guidelines’ than actual rules.”
David