Will BNO status holders and their dependants be required to make any additional applications after their arrival before they will be allowed to apply to work and / or study?
The right to work and / or study will be part of the BNO visa. Even Hong Kong BNO status holders and their dependants coming to the United Kingdom before the visa scheme goes live on 31 January 2021, and have been granted leave outside the Rules to wait for this date, are allowed to work and / or study. https://www.hongkongwatch.org/all-posts/2020/10/23/qampa-the-bno-visa-scheme-what-we-know-so-far#:~:text=The%20right%20to%20work%20and,to%20work%20and%20%2F%20or%20study.
"What if you choose to arrive in the UK using this 6-month stay (i.e. before the BNO Measures are in force)? You may be granted leave to remain outside of the Immigration Rules for six months, during which you can work and study. However, you will not be able to use the NHS (except for limited free service), and you will be required to have full health insurance for you and your dependants for the full period of your leave to remain outside of the Immigration Rules. The UK Government has indicated that there will be a mechanism for BNO holders in the UK to apply for leave to remain under the BNO Measures.
"What if you choose to arrive in the UK using this 6-month stay (i.e. before the BNO Measures are in force)? You may be granted leave to remain outside ...