You can check it by user id profile;u=
1. First Bitcointalk profile is admin https://bitcointalk.org/index.php?action=profile;u=1
2nd user doesn't exist anymore,
3rd is satoshi https://bitcointalk.org/index.php?action=profile;u=3
4th sirius https://bitcointalk.org/index.php?action=profile;u=4
5th doesn't exist anymore
6th nandnor https://bitcointalk.org/index.php?action=profile;u=6
7th, 8th and 9th doesn't exist anymore.
10th Xunie  https://bitcointalk.org/index.php?action=profile;u=10
As you can see, none of earliest Bitcointalk users isn't anymore, some of them accounts were deleted. Only Xunie had signed in in 2019.
2. I'm lazy to check merit ttranactions on mobile, but I'm almost sure that this theymos post got merit first:
https://bitcointalk.org/index.php?topic=2818350.0. But I don't know who is first merit sender.