No. The simplest example is a matter-dominated universe at exactly the critical density. It decelerates forever but never quite stops expanding--the expansion rate asymptotes to zero.

I assume decelerating forever means asymptotically approaching not collapsing.

An object on an escape trajectory from another mass is forever decelerating, but it still escapes.

Would it not enter the viscinity of other objects which would eventually coalesce into local centers of mass (maybe like one per observable universe diameter or something)?

Nope, cosmic Zeno's Paradox. Collapse never quite happens.

Nope, that would be velocity changing sign, which means acceleration would increase.

No, in much the same way that a speeding vehicle slowly decelerating towards a stop doesn't mean that it will return to where it started the journey.

Actually it's worse than that, "decelerating forever" doesn't even mean that it ever even comes entirely to a stop. let alone return to where it started.