If you're going to try to downgrade TFS, you probably should not downgrade 0.4 unless you have a very specific reason for using 0.4, instead use a newer TFS version like 1.3.
Downgrading is (probably) a lot of manual work, you should probably start out in protocolgame and remove the parsing and sending of protocol codes you don't need, then find out where all these protocolcodes originate from and try to disable the features all-together.
If you don't know what you're doing, you should probably try to hire someone to do it for you instead, or look for a server that's already downgraded or old version of OTServ/TFS or any other OTS and compare the source files between v8.6 and the version you wish to downgrade to.
There's no tfsdowngrader.exe.
