CS -” Vehu Yegaleinu” It does not mean that the Rebbe is Mashiach, If it did, then the Rebbe’s Moshiach would be the frierdicke Rebbe – he’d have a different mashiach than all of us,
(Many Chabadniks answer that whenever the Rebbe said “Friedkier Rebbe” he was referring to himself. But that’s a gross simplification. In actuality, he was refering to the Freidiker Rebbe, because he was the Rebbe’s rebbe. But Chassidim apply whatever the Rebbe said on the Friediker Rebbe to the Rebbe, because he’s our Rebbe.)
Rather vehu tegaleinu is referring to an Arizal who asks that the gemara promises a reward of seeing the Geula for many mitzvois. He asks, how can that be true, many people have kept those mitzvos but were niftar? So he answers that before techiyas Hamaysim, tzadikim who kept those mitzvois will have techiyas hameysim before the geula.
With this, we can explain what will happen when mashiach comes “Veyasu Kulam Aguda Achas”. When Mashiach comes, all the talmidim of each tzadik will line up behind his tzaddik. For example, all the Breslovers will line up behind Rav Nachman, All Sefardim behind Rav Ovadia etc, and those tzadikim will line up behind their Rebbe – Rav Ovadia behind Rav Ezra Attias, Rav Nachman behind Rav Baruch etc, and their rebbe behind his rebbe, and so on until Moshe Rabeinu, who will line up behind Mashiach,
Thus, when Mashiach comes, the Rebbe will be resurrected and lead his talmidim to the geula, and he’ll be behind the Riyatz, and he’ll be behind the Rashab etc etc.
And that’s how Vehu Yegaleinu applies to us in regards to the Rebbe, and to the Rebbe in regards to the Friyidiker.