Strange? Came across a question for which best answer awarded and posted 3 months ago but answering is still allowed on it?

That's not strange at all. That's how the site is designed, because a selected BA may not actually be the best answer there is for a question. For a while the site was programmed to close questions to new answers after 7 days, but that didn't last long (and ended early 2018).

Users who post after a BA has been selected don't get 2 pts for their answer, but their post does count against the total # of answers they are allowed to post each YA day.

Questions are open forever and can continue to be answered even after a Best Answer has been chosen.

That's been possible for the last 5 YEARS. So has answering your own question. Check the YA blog, available under the "About" option at the bottom of the left column.

Where have you been? Verizon has owned YA for 2 years. Do you have 5 year or more memory gap or senior moment, or have you just recovered from the chaos of Trump et al.and or Brexit sucking the oxygen from the room and returned to reality?

Questions can always be answered, they never close.

That went away for a short while, but then came back. They may change it back to 7-day limits at any time. They never tell us.

A lot of changes have been made throughout the years ... some not good

YA glitch

Yes, you can still answer old questions even if BA has already been chosen. We've been able to do that for quite a while now.