CONO-SUR 2021 Problem 1

We say that a positive integer is guarani if the sum of the number with its reverse is a number that only has odd digits. For example, $249$ and $30$ are guarani, since $249 + 942 = 1191$ and $30 + 03 = 33$ . a) How many $2021$ -digit numbers are guarani? b) How many $2023$ -digit numbers are guarani?