Is this the correct w recognize Opcodes for a DIY 8bit Processor
Yes this can work.  In general you can recognize any bit pattern by inverting the zeroes while leaving the ones unchanged, and then feeding all those bits into an AND gate.  The result will be 1 only when the pattern matches.
There are also other methods.  For example invert all the 1s while leaving the zeroes unchanged and feeding all those bits into an OR gate.  In this case the result will be 0 only when the pattern matches.
Another approach for matching a 4-bit pattern would be to use a 16:1 multiplexor with the input bits attached to the mux address lines.  You place zeros on all the data inputs except for the one address you want to match.