Wine competitions come in all shapes and sizes. Some are for that year's wines, other are for wines from a specific older year. You would have, if I recall your palate accurately, loved to partake in this CdP tasting of the 1998 vintage. (https://www.erobertparker.com/members/ews/ews195.asp) . There is no rule per se to the age of wines in a competition.

Tannins soften over time in the bottle. Many New World producers are picking later and later so as to get softer tannins right at release rather than waiting. Many f the very expensive and popular Bordeaux wines are laid done for so long because hey were not picker late in the season and need much bottle age to really get the tannins to soften and the vegetal characteristics to diminish.

The big changes to a wine when exposed to air are the fruit flavors and aromas. The newly introduced presence of oxygen in the wine will also cause a variety of other changes but i general the mingling of air and wine is first noticed in the aromas then the palate.

My cellar is a bit of a baby unfortunately. Most of it is not even 20 years old.