A supported decision-making agreement is valid if

1. (1) the agreement is dated and in writing;
2. (2) the agreement satisfies the requirements of AS 13.56.010 — 13.56.050;

3. (3) the agreement has been signed by the principal and each named supporter, including any alternate supporter, and the

   1. (A) signing takes place in the presence of two witnesses who also sign the agreement; or
   2. (B) signatures of the principal and each named supporter, including any alternate supporter, are notarized; and
4. (4) when the principal has a guardian or conservator, the principal has notified the guardian or conservator of the agreement.