Hi,
As questions 1 & 2 of your query relates to Inheritance Tax, we would advise to contact the Inheritance Tax department on 0300 123 1072 from the UK or +44 300 123 1072 from abroad, or send in a letter to Inheritance Tax, HM Revenue and Customs, BX9 1HT, United Kingdom.
In regard to declaring dividends less than £2,000, this would depend on their individual circumstances and where such dividends have arisen from.
We would suggest checking the Self-Assessment criteria tool:
Self Assessment tax returns
Thank you.