Did all the Strangers have access to John Murdoch's memories in Dark City (1998)?

It's a little more complicated than that. The other strangers appear to be able to see what Mr Hand is thinking (and the memories he's accessing) but without any ability to control those memories. They're relegated to the position of observers.

Mr. Wall swallowed his annoyance for the common good. “Indulge us, Mr. Hand . . .” he murmured as if speaking to a child. “If you were Mr. Murdoch, yes?”

A faraway look fell over Mr. Hand’s pale features like a curtain. The others knew what was happening. Mr. Hand was remembering.

“If I were Mr. Murdoch—I would . . . remember how my wife had hurt me, by sleeping with another man,” Mr. Hand said softly.

The Strangers watched with awe—and envy—as images bubbled up in Mr. Hand’s mind . . .

_{^{Dark City: Official Novelisation}}

Note that while they have a hive of shared memories, the Strangers aren't necessarily controlled by a single cohesive force. They have personalities and drives that are unique to each individual alien, hence why Mr Hand is able (and willing) to volunteer to be the one imprinted with the memories of John Murdoch.