Talmud Bavli in Chagigah 15a says:
ת"ר מעשה באחר שהיה רוכב על הסוס בשבת והיה רבי מאיר מהלך אחריו ללמוד תורה מפיו אמר לו מאיר חזור לאחריך שכבר שיערתי בעקבי סוסי עד כאן תחום שבת א"ל אף אתה חזור בך א"ל ולא כבר אמרתי לך כבר שמעתי מאחורי הפרגוד שובו בנים שובבים חוץ מאחר
The Gemara cites a related story: The Sages taught: There was once an incident involving Aḥer, who was riding on a horse on Shabbat, and Rabbi Meir was walking behind him to learn Torah from him. After a while, Aḥer said to him: Meir, turn back, for I have already estimated and measured according to the steps of my horse that the Shabbat boundary ends here, and you may therefore venture no further. Rabbi Meir said to him: You, too, return to the correct path. He said to him: But have I not already told you that I have already heard behind the dividing curtain: “Return, rebellious children,” apart from Aḥer?
(Sefaria)
I'm focused on the text "חוץ מאחר" ("apart from Aher"). In the Talmud Yerushalmi there is a similar story but the wording is slightly different.
א"ל דייך מאיר עד כאן תחום שבת א"ל מן הן את ידע א"ל מן טלפי דסוסיי דהוינא מני והולך אלפיים אמה א"ל וכל הדא חכמתא אית ביך ולית את חזר בך א"ל לית אנא יכיל א"ל למה א"ל שפעם אחת הייתי עובר לפני בית קודש הקדשים רכוב על סוסי ביה"כ שחל להיות בשבת ושמעתי בת קול יצאה מבית קודש הקדשים ואומרת שובו בנים חוץ מאלישע בן אבויה שידע כחי ומרד בי (Sefaria)
Rather than saying "except for Aher" it says "except for Elisha ben Abuya". Is there any significance here between the voice using his actual name in Talmud Yerushalmi versus using the term "Aher" in Talmud Bavli?
Also, how do we reconcile the voice saying that Aher or Elisha ben Abuya (depending on which account you are reading) cannot repent. The Rambam says in the Mishneh Torah, Teshuva 3 that someone who denied Hashem his entire life can repent before his last breath and have a share in the World to Come:
בַּמֶּה דְּבָרִים אֲמוּרִים שֶׁכָּל אֶחָד מֵאֵלּוּ אֵין לוֹ חֵלֶק לָעוֹלָם הַבָּא כְּשֶׁמֵּת בְּלֹא תְּשׁוּבָה אֲבָל אִם שָׁב מֵרִשְׁעוֹ וּמֵת וְהוּא בַּעַל תְּשׁוּבָה הֲרֵי זֶה מִבְּנֵי הָעוֹלָם הַבָּא שֶׁאֵין לְךָ דָּבָר שֶׁעוֹמֵד בִּפְנֵי הַתְּשׁוּבָה. אֲפִלּוּ כָּפַר בָּעִקָּר כָּל יָמָיו וּבָאַחֲרוֹנָה שָׁב יֵשׁ לוֹ חֵלֶק לָעוֹלָם הַבָּא שֶׁנֶּאֱמַר (ישעיה נז יט) "שָׁלוֹם שָׁלוֹם לָרָחוֹק וְלַקָּרוֹב אָמַר ה' וּרְפָאתִיו". כָּל הָרְשָׁעִים וְהַמּוּמָרִים וְכַיּוֹצֵא בָּהֶן שֶׁחָזְרוּ בִּתְשׁוּבָה בֵּין בְּגָלוּי בֵּין בְּמַטְמוֹנִיּוֹת מְקַבְּלִין אוֹתָן שֶׁנֶּאֱמַר (ירמיה ג יד) "שׁוּבוּ בָּנִים שׁוֹבָבִים".
That is saying, that none of these will have a share in the World to Come, if he dies without repentance; but if he repent from his wickedness and died in a state of repentance, he is, indeed, of the sons of the World to Come, as there is not a thing to stand in the way of repentance. Even if one who denied the existence of God all of his life but in the end repented, has a share in the World to Come, for it is said: "Peace, peace, to him that is far off, and to him that is near, saith the Lord; and I will heal him" (Is. 57.19). All of the wicked, and apostates and their like who turned in repentance, whether publicly or secretly, should be accepted back into the folds of Israel, even as it is said: "Return ye backsliding children" (Jer. 3.22) (Sefaria)
I've tried to reconcile this and perhaps in Talmud Bavli the reference to Aher means something more significant (as he did not say "Elisha ben Abuya" could not repent, but rather the "Aher" or "other" could not repent; i.e., if he stops being an "Aher" then he can).
Are there any commentaries that discuss this or perspectives?
In sum: 1) Do any commentaries address the difference between Talmud Bavli and Yerushalmi as I described? 2) Do any commentaries address the idea that the Talmud seems to suggest that he cannot repent which runs contrary to the idea that all can repent? 3) Anywhere else in the Talmud or any other perspectives that anyone here thinks would be helpful in understanding this?
Thank you!