If somebody has a longer type of beard that grows well beyond the chin I.e. the beard extends down the start of the neck area or towards the mid part of the neck, is it obligatory to wash/ensure water reaches every part of the beard for wudhu or is it sufficient to wash to the part of the beard that reaches the furthest part of the chin and leave the part that reaches the furthest part of the neck?

It is only required to wash the part that is at the bottom/tip of the chin, but it doesn’t hurt to pass the hand over the rest of the beard anyway.