Norm's right; you are getting into deep water if you can't tell one from the other. The fuel line runs to the fuel pump; the brake lines to the brakes. Neither should be messed with by patching. In the event you patched a brake line with a hose suitable for fuel, the line would at least bulge, if not burst when you applied the brakes.
Please let an expert look at your 'corroded' lines, and take it from there.
There is a lot of great advice on this forum; keep in touch.
regards,
Mark