2 Gamertag Bug/Glitch

It is showing my old gamertag when im chatting with friends, on the xbox app and on the xbox home screen, on the profile screen it shows both on the xbox and the xbox app, and in all games, in the gamepass iOS app, and on xbox.com profile page it shows the new one. when i go to a few gamertag checkers, it shows that my old one is free and my new one is taken by me so it is definitely a bug. We called microsoft support like 5 times with no fix. I have seen many other people online with the same issue.

May I ask what do you mean by showing the older gamertag? If you mean like the examples HERE (Mobile App) and HERE (PC App), that is normal. As for parties, from personal experience on the Xbox One, it has shown my system gamertag Madam Sukii. Lastly, for the system menus like your second screenshot above, that's normal.

Everywhere (including all games even series x games show the new gamertag but in parties/chat, on the homescreen, in the xbox app, and in the system menus show the old one.

This is apart of the new gamertag system and not a bug. Alecminichini is the gamertag that'll appear in game for games that don't support the gamertag change. While Alecapple will appear in games that do support the gamertag change (Which is a small portion).

Give the developers a week or 2 to fix any bugs/glitches~