LT Spice cant find definition of model
It's a little bit of an obscure error telling you that ako is not allowed inside .subckt definitions -- they must be in the top level schematic, only.
The solution, if you have to use those transistors, is to:

RClick on a transistor, select the row of the desired transistor, then press Ctrl+C -- this will copy the .model definition
Esc twice, to avoid making changes to the transistor
S to bring up the SPICE directive editor
CtrlV to paste the copied .model
before pressing Enter, modify the name to be MyNPN, or MyPNP, or whatever name you wish
make whatever other modifications to the parameters
either press Enter or click the OK button
LClick to place the SPICE directive in the schematic

This goes the same way for both the NPNs and the PNPs. Or, if those transistors are not mandatory, simply add your own .model definition for each, but not with the ako flag. Now it should work.
However, looking over your schematic, it looks like you prepared V(a) and V(b) but they are not used anywhere. They will also reside inside the subcircuit, together with the power supplies -- this is not usually done, but that doesn't mean you can't go wild with it, topology included.