Voluntary NI contributions and overseas work - Class 2 or Class 3

Hi As I understand there are rules around making NI voluntary payments if you were overseas. From reading the HMRC guidance I understand that to qualify for the reduced Class 2 Contributions one must : - Have been working in the UK for at least 36 months immediately prior to going to work overseas. Is this correct ? So if in the case that I left the UK in 2000 to work then returned in 2005 to work full time and left in 2006 to work overseas. I cannot pay class 2 for the catch up period of 2006 to 2023 and should pay Class 3.

Any advice on above ?

Hi,
To pay voluntary class 2 National Insurance contributions you must be employed or self-employed overseas and were normally employed or self-employed in the United Kingdom before your departure.  
If you could read our leaflet NI38 ‘Social Security Abroad'  complete and return our CF83 application form then our International Team will be able to assess whether you may be entitled to pay at the voluntary class 2 rate.
Thank you.