(compared to the) same period of the preceding year ... (also : im Vergleich zum Vorjahreszeitraum)

... außer auf EU-Seiten ist diese Wendung auf jeden Fall auf UK-Seiten zu finden :

making imports of certain hot-rolled flat products of iron, non ...

https://www.legislation.gov.uk/eur/2020/1686/...

... Turkish import volume in the period June-mid-October 2020 with the monthly average volume of imports in the same period of the preceding year 2019.

Lessons from the collapse at GE - Imperial College London

https://www.imperial.ac.uk/business-school/ib...

29 Jan 2019 — In the first three quarters to June 2018, 32 gas turbines were ordered from GE, compared to 51 in the same period of the preceding year.

3rd Quarter Results - Zhejiang Southeast (BQ36) - InvestEgate

https://www.investegate.co.uk/zhejiang-southe...

25 Oct 2002 — If compared to the same period of the preceding year, the electricity sale during the third quarter decreased by 0.121 billion kwh, ...

Hier würde ich - für Vorvorjahr - dann eher die Jahreszahl nennen : (compared to the) same period of the year [nnnn -2])

https://www.ons.gov.uk/economy/economicoutput...

Year-on-two-year change in sales and jobs in small businesses, UK, January 2019 to October 2021

But note that you can only use this as in this example: as an adjective before a word like "change".

Microsoft Word - Currys plc - 2021-22 Results Statement - FINAL.docx

I'd never heard of "Year-on-two-year" before but this statement contains some examples where it's used as a table heading (year-on-2-year).

#5 Yes, "year-on-three-year" appears to be used. Here's an example: Decline in sales volumes "not seen since depths of pandemic" (brc.org.uk)

I guess, as this article implies, that "year-on-two-year" and "year-on-three-year" came into usage during the pandemic because comparisons with lockdown years were misleading or uninformative.