The ABS lights can come on for a number of reasons, not least of which could be the condition of the battery, although I can't think why it should happen after travelling 500 metres. You may just get away with resetting the ABS system, the attcahed link shows how ou can do this ith ABS1 and ABS2, what harm could you possibly do? (answer; plenty, but the narator seems to know what he's talking about)
BMW Motorcycle ABS II Reset
On a 1997 and 1998 BMW K1200RS gearbox oil should be inspected each 20,000km. Changing the oil is very easy, and shouldn't take more than a few minutes as it down't look like the side panels need to be removed.
As for the lever sticking at 3rd gear, try lubricating the selector. If it is a more serious problem then you may need to rebuild your gearbox. However I would put up with the problem for as long as you can.
Will depend on year, later models use a CanBus system, which replaced the fuse box, hence no fuses. If something trips the canBus acts like a fuse to protect what ever caused it to trip, turning off the ignition for 30 secs and back on again resets the system.
It may be a throttle lock. to find out, turn the throttle (ENGINE OFF) and hold it while tightening the screw. it should keep the throttle from closing when you release the grip. This is a very dangerous thing and should not be used EVER.
Usually, a rapid or immediate loss of power is indicative of a major component failure on an engine...and its something you should consider. Some tell tale signs, smoke out of the exhaust (note the color); or severe noises like loud banging and knocking- time for a major engine repair / over-haul.
On the other hand, perhaps what is happening is just coincidental to some other problem that was already in the making and was exacerbated when you snapped open the throttle.
Check the gas flow from the tank through the delivery system and filter- check the fuel shut-off valve, make sure it's fully open and that it is free of any clogs which would prevent the full flow of gas to the carburetor. Check the carburetor, see if the float bowl is full of gas; if necessary, check for a faulty fuel pump.
Another remote possibility is stale gas- was the bike sitting in storage for a while or did you use gas from a can that was lying around in storage...especially if it is of an ethanol blend that absorbs moisture.
Check the electrical system for ground shorts, spark plug cables for any deterioration and intermittent spark, check the CDI for either a weak, no-spark or verify a strong spark; and so-forth.
If everything is so far okay, inspect the engine oil; it should look smooth, glossy, and somewhat transparent. and run some compression tests.
Best regards.
With that mileage I would look at the wiring from the ignition switch. Start her up and have a good wiggle to see if it cuts out. This part of the loom can be replaced/repaired and it is not an uncommon problem. Peel back the outer sheaf, you may find a lot of green corrosion here and fragile wiring.
The other option would be a failing hall effect sensor (HES), but check the wiring first.
