Materiality applicable to reliance on same conviction for s 501(3A)(a)?

The relevant facts are as follows:

1. In 2015, the Appellant was sentenced to a term of imprisonment of more than 2 years (the 2015 sentence);
2. In 2016, a delegate was satisfied that s 501(3A)(a) of the Migration Act 1958 (Cth) was met on the basis of the 2015 sentence of imprisonment and therefore cancelled the Appellant's visa (first cancellation);
3. In January 2017, the first cancellation was revoked under s 501CA(4) of the Act;
4. In October 2020, the applicant was sentenced to an aggregate sentence of 16 months imprisonment (the 2020 sentence);
5. In December 2020, a delegate again mandatorily cancelled the applicant’s visa under s 501(3A) (the second cancellation). The delegate was satisfied that s 501(3A)(a) was met on the basis of the 2015 sentence. The 2020 sentenced relied on only in satisfaction of s 501(3A)(b).
6. In September 2021, a delegate refused under s 501CA(4) to revoke the second cancellation;
7. In November 2021, the Tribunal affirmed the decision of the delegate not to revoke the second cancellation;
8. The applicant applied to the Federal Court (FCA) for judicial review of the second cancellation, which is said to be invalid, with the result that there was no power for the delegate or the Tribunal to exercise in relation to revocation of the second cancellation.

Some of the questions to the FCA were as follows:

Question 1: Can the cancellation power in s 501(3A) be exercised more than once in respect of the same failure to pass the character test in s 501(3A)(a)?

Question 2: If the answer to Question 1 is 'yes', can it be said that an error in exercising the power in s 501(3A) more than once in respect of the same failure to pass the character test in s 501(3A)(a) would not be material if a separate conviction and sentence existed which, although not relied upon for the purpose of s 501(3A)(a), on its face met the threshold of the Minister being satisfied as to an applicant having "a substantial criminal record"?

Question 3: If the answer to Question 2 is 'yes', and putting to one side the Migration Amendment (Aggregate Sentences) Act 2013 (Amending Act), can it be said that the 2020 sentence did not render the error immaterial, as the Full Court's decision in Pearson is such that aggregate sentences cannot be relied on to satisfy s 501(6)(a)?

Question 4: Is the question of whether or not a decision is affected by jurisdictional error and therefore to be declared invalid to be considered by reference to the law existing at the time that the declaration is to be made, instead of by reference to the law existing at the time of the decision?

Question 5: Is Pearson applicable in this case in spite of the Amending Act, as items 4(1) and 4(3)-(4) in Pt 2 of Sch 1 to the Amending Act retrospectively validate decisions that are invalid “only because a sentence, taken into account in [making the relevant decision] was imposed in respect of 2 or more offences” and as the underlying error stems from the fact that the delegate relied on the same sentence of imprisonment as had been relied upon for the first cancellation decision, instead of stemming from reliance on an aggregate sentence?

The FCA answered those questions as follows: