Expression for currents and potential over a resistor when switch is opened at t = 0
Conventionally I would solve with initial conditions, at \$t = 0^+\$ I have \$i_R(t) = 2\$ since we know the current in an inductor cannot change instantaneously, and so at the opening of the switch, all the current is delivered to the resistor only.


You should think of the initial condition being the state of the inductor current.

$$i_L(0)=0$$

Since the inductor current doesn't change instantaneously, there's no need to distinguish \$t=0^-\$ from \$t=0^+\$.


  which is correct but this does not make sense to me as it has derived information from the \$t &gt; 0\$ circuit and solved for the \$t &lt; 0\$ circuit


You know that \$i_L(0)=0\$ because of information about the \$t&lt;0\$ circuit, not the \$t&gt;0\$ circuit, so there's no contradiction.