How to justify that op-amp 1 has negative feedback?
Apply "up-down thinking". This is a way of reasoning about which way quantities like voltages and currents will change if a circuit is disturbed in some particular way.

Assume that there is in fact negative feedback and so the circuit is stable with \$V_i\$ and \$V_o\$ at zero volts (on a dual-voltage supply).

Now, what happens if \$V_i\$ increases slightly? Which way will the output \$V_o\$ move, and how does that propagate through OA2 to influence the + input of OA1? Does the + input move in the same direction as -, or against it?

If + follows -, is that negative feedback or positive feedback?