Which tax year should unemployment benefits reported?

The question is summarized in the title:

Unemployment benefits are reported for the tax year in which (choose one):

1. the week of unemployment occurred;
2. the week was claimed;
3. the benefit payment was initiated; or
4. the benefit payment was received

For example:

1. Claimant is unemployed in May 2020.
2. After a lengthy appeals process concluding in late December, claimant claims the week in May (or multiple weeks in May) on December 31, 2020. (The claimant was not allowed to claim the week until the appeal was won; see note below.)
3. On the same day (December 31, 2020) the state agency computer system automatically approves the claim of the week in May and initiates the direct deposit (as I understand, it’s an automated clearing house (ACH) transaction).
4. The money appears in the claimant’s bank account on January 1, 2021 (or possibly January 2 because of the bank holiday).

Does this payment go on the 2020 tax return (filed in 2021) or on the 2021 tax return (filed in 2022)?

Does the answer change or become more definite if the claimant claims the week on January 1, 2021 in Step (2)?

(Note that, normally for Regular Unemployment Insurance (1) and (2) more or less coincide (a week is usually claimed in the immediately following week), but for Pandemic Unemployment Assistance (PUA), at least in my state, a person cannot claim a week until they are pre-authorized to claim that week, at which time the claimant can claim the week (retroactively).)

Edit:

I did a bit more research using better search terms (previously I was getting only superficial or irrelevant information returned), and I think the answer is probably (4), unless there is some provision of law relating specifically to taxation of unemployment benefits that I don’t know about. That being said, to avoid scrutiny, it’s probably best if reported income matches the 1099-G form, even if (3) and (4) are technically different. Sources:

• 26 U.S. Code § 85. Unemployment compensation ("gross income includes unemployment compensation")
• Taxable income computed by date earned or pay date? Personal Finance & Money Stack Exchange ("constructive receipt" of income [including, I think, income from unemployment assistance])