Decrease national dex to 250 fire red hack

Hello all, is there a way to adjust prof oak's script using xse to have the national pokedex completed at 250? I'm doing a hack that only focuses on gens 1 and 2.
And once completed, can I insert a trainer battle with prof oak? (I've already made a battle with him a separate encounter, just wanted to give a bit more of a reward than wroooaaaaarrr!!

Hey! If you look at Oak's script, specifically this section here:

special2 LASTRESULT 0x1B0
compare LASTRESULT 0x0
if 0x1 goto 0x81A7470
compare LASTRESULT 0x1
if 0x1 goto 0x81A747E

Click to expand...

That special2 command checks if the National Dex is complete. You could do some digging with a hex editor to edit the special and change the number required for completion, but I'll assume you might want a slightly quicker/beginner friendly solution, by changing that snippet above to this:

setvar 0x8004 0x0
special2 LASTRESULT 0xD4
buffernumber 0x0 0x8006
compare 0x8006 0xFA
if 0x1 goto 0x81A747E

Click to expand...

It's been some time since I hacked FR but if I recall correctly that's similar to how Oak's aides check for a certain amount of Pokemon caught. It's not the best solution by far, but hopefully it shows how you can repurpose some things to make them fit what you need =)

As for the battle part, you sure can, just check out the trainerbattle command and how to use it, and you should be good to go!