Suppose that implies Abaddon's Otis then? 😁
As to the changing modes question, here's an answer I found from the Living Errata.
“Entering Squad Mode is an action that effects the group, not just an individual. If a Battle-Brother successfully enters Squad Mode all other Kill-team members within Support Range may (if they choose) immediately enter Squad Mode without using Full Action or passing a Cohesion Challenge. If the Kill-team becomes separated during the Mission its members may form multiple Squads for the purpose of Squad Mode abilities so long as all the requirements of entering Squad Mode are met and the Support Ranges of the multiple squads do not overlap.”
So someone would need to be in Support Range and we'd need at least 1 Cohesion, then someone takes a Full Action (or a Reaction by passing a Cohesion Challenge) to chance into Squad Mode.
A Battle-Brother drops out of Squad Mode—and returns to Solo Mode—at the start of his Turn if:
• He falls unconscious or dies.
• His Kill-team’s Cohesion is reduced to 0.
• He is no longer in Support Range of at least one other
member of his Kill-team.
• He chooses to return to Solo Mode.
In certain circumstances he may also lose Squad Mode if he fails a Cohesion Challenge (see page 212).