When is the Torah scroll to be returned to the ark on Rosh Chodesh?
Chabad custom: The authentic and traditional Chabad custom follows the custom of the Sephardim to return the Sefer Torah to the Ark only after Uva Letziyon. However, some Shul’s of Anash return the Sefer Torah to the ark immediately after Gelila is completed, even prior to saying Ashreiy and completing Uva Letziyon, as is the Ashkenazi custom. Seemingly, this is an error, although since the Chabad custom is for the Chazan not to complete Uva Letziyon aloud, practically the following order should be followed: After Gelila, the Chazan and congregation should recite Ashrei and Uva Letziyon to themselves. As soon as the Chazan completes Uva Letziyon to himself, he is to say Yehalelu, signaling the bringing of the Sefer Torah to the Aron.
 Michaber 423:3; Second opinion in Tur 150; Siddur Admur; Custom mentioned in Admur 25:39; 1st custom mentioned in Rama 25:13; See Shaar Hakolel 22 [p. 39]
 The reason: As the Divine light drawn down through prayer concludes after the entrance of the Sefer to the Heichal and we hence desire to delay this as much as possible. [Shaar Hakolel ibid; See however Kaf Hachaim 135:2 in name of Shaar Hakavanos that states it is for this reason that we return the Sefer Torah immediately after the reading]
 Levush 423; M”B 423:5; See Kaf Hachaim 423:11; This is based on the ruling of the Rama 25:13, and Ashkenazi custom [1st opinion in Tur 150], that by all days of Torah reading the Sefer Torah is returned to the Ark immediately after the Torah reading, and the same would apply to Rosh Chodesh. [Poskim ibid]
 The reason: Some say the reason behind this custom is because not all people are able to delay removing their Tefillin until after Uva Letziyon and it is hence returned beforehand. [Ashel Avraham Butchach 149:1] Alternatively, it is a Mitzvah according to Kabala to return the Sefer Torah to the ark immediately after the reading. [Kaf Hachaim 423:11; 135:2 based on Arizal]
 Siddur Admur regarding Rosh Chodesh “Afterwards one says Ashrei and Uva Letziyon and enters the Sefer Torah to the Heichal”; Hiskashrus 457 p. 18; Siddur of Rav Raskin p. 482; Likkut Dinei Rosh Chodesh 7:15
 Background of this Chabad custom: In the Siddur of Admur he writes explicitly to return the Sefer Torah on Rosh Chodesh after Uva Letziyon, and so was the Chabad custom in all places until the year 1988. From the year 1988 it became accustomed in 770 to return the Sefer Torah to the Ark immediately after Gelila and not to wait for Uva Letziyon to be recited. This is unlike the Chabad custom followed throughout the year on Mondays and Thursday’s, which follows the ruling of the Michaber. Some suggest the reason for this custom is because it is not our custom to end Uva Letziyon aloud in order to avoid the necessity to say Kaddish immediately afterwards [see next Halacha] and hence in order to negate a mistake the custom became to immediately return the Sefer Torah to the Heichal, hence signifying the conclusion of the Chazan’s part of Davening. [See Hiskashrus 466 p. 15] However, perhaps in truth one can say that the Chazan in 770 already completed Uva Letziyon to himself by the time Gelila had ended and hence said Yehalelu for it to be brought, and from there began the mistaken custom of always saying Yehalelu as soon as Gelila is complete even prior to the Chazan, or anyone else, finishing Uva Letziyon. Whatever the case, no proof for Chabad practice and custom can be brought from the custom of the Minyan in 770 even if the Rebbe Davened there, as is well known that the Rebbe [as did also the Rebbe Rayatz and Rebbe Rashab] did not intervene with the practices of the Minyan, and many things they did were in fact contrary to his opinion. [See Yoman of Rav Groner where many such instances are recorded that the Rebbe privately complained to him of certain customs that the Minyan decided to follow. To then treat these customs as if they are official Chabad practices with the Rebbe’s approval and desire, is nothing less than sacrilege, in addition to being inaccurate; See Sichas Matos Maseiy 5740 p. 655 that the Rebbe takes no responsibility for what happens during Davening in 770; Al Minhagim Umikoroseihem [Bloy] P. 22]
 See previous footnote; I am not aware if the Rebbe gave his approval for the above custom and as to the events surrounding its first initiation, and even if such approval was given, it remains to be verified that whether the approval was only after the Chazan finished saying Uva Letziyon to himself, in which case the custom is understood, and even if approval was given for it to be done before the Chazan finishes Uva Letziyon, it is unclear if this was due to private personal reasons relevant specifically to 770, or as an intent to change the entire worldwide Chabad custom. In conclusion, anyone who desires to follow this custom in change of the Chabad practice of generations, and the explicit ruling of the Alter Rebbe, the burden of proof is on him to show that the Rebbe explicitly approved of such a practice even if the Chazan did not yet finish Uva Letziyon or even begin Ashrei, and for reasons relevant to worldwide Chabad Jewry and not specifically to his Minyan. Practically, being that none of the above matters have been verified I don’t see any basis for Chabad Minyanim to change from the traditional custom, other than ignorance of all that was discussed above, or Shpitzkite, of which both have no place in Halacha.
 See Hiskashrus 795, 782, 786 based on the widespread Chabad custom today, based on an oral directive of the Rebbe in his Minyan