Hello @Repavo6,
when you unlink a platform account from your EA account, you will lose most of your progress and content from your Apex account - this is specifically pointed out in the article regarding unlinking platform accounts.
You will have to connect them to your original accounts, if you want your progress back, for which you will need to contact EA Support as you cannot unlink accounts yourself within the next 6 months.
https://help.ea.com/en/help-home/
And no, what you were thinking of doing will not work, as any Apex account made past the 20th of October will not be merged (and you don't have your progress on this account now anyway, so there's nothing to merge).
You can read up on it here again:
https://answers.ea.com/t5/News-Game-Updates/CROSS-PROGRESSION-IN-APEX-LEGENDS/m-p/13131198#M172
Bitte schickt mir keine Direktnachrichten für Support - taggt mich im Forum @EA_Pythia