I don't think patching would make any difference to anything. Fonline needs access to the master.dat and critter.dat because it uses the sprites, graphics, tiles etc. Other than that they're separate programs. As long as Fonline 2238 has access to those dats, it shouldn't care if Fallout 2 is even installed any more.
Can you explain :
1) Exactly what you're trying to do?
a) Use / make mods for Fallout 2?
b) Play Fallout 2?
c) Play Fonline 2238?
d) Something else?
2) What you've tried, and how / why it's not working?
i.e. if you're trying to run Fonline 2238, does it say "master.dat not found", or something suchlike? Are there any error messages? What operating system are you trying to run this on? Windows? Linux? Sega Master System?
3) Is English your first language? If not, you may find it easier to explain your problem in one of the other language subforums, be able to get help from someone here who speaks the same language as you, or maybe look on one of the completely separate Fallout/Fonline forums in relevant language.
4) Any other technical information which would clarify what you're trying to do and what is happening.
Basically, if you can explain clearly exactly what the problem is, then someone will probably be able to help you. Most problems related to getting this program to run will have been seen before and solved.