I have a 1999 passat estate and i need to change the faulty tailgate handle,unfortunately i can no longer open the tailgate to access the inside of the tailgate/back of the handle assembly,how can i open the tailgate with the minimum of damage?,help please.

You should be able to feel around and locate that rod. After you get it you can use some pliers or vice grips to put on the rod to release the lock on that side and the handle on the other side.
As long as the locks and the rods move freely and are in good shape then all you will need is a new handle asm. It will come with new clips and on the other side of the tail-gate are 3 torque-head screws that will need to be removed to replace that handle.

The opening of the boot by key or remote is done via an electric motor,you may have a faulty motor or you may have water ingress through the boot handle which has corroded the terminals, this is quite common.

Under waranty? Back to the dealer. Out of waranty? Either a dealer, or a private shop that has a good reputiation. Ask your friends amd co-workers and family.

Child locks only disable the INSIDE handle leaving the OUTSIDE handle operating. Sounds like the linkage for the outer handle has come apart.

The linkage to the exterior handle most likely broke off at the handle or the linkage clip broke

Make sure the e-brake is completely dis-engaged; handle all the way down/pedal all the way up - if pedal; pull release and lift up on the pedal.

If problem with the ABS light continues you'll have to take the car to a qualified mechanic to test the ABS sensors...could have one bad/mis-aligned.

You'll need to remove screws that are by the door handle, arm rest, under door and side of door and then gently pull back on the panel as there will also be retaining clips attached and you don't want to break them. If needed, you can pull back the weather seal (can't reuse it, but it's not that important) and you will be able to access everything inside the door

either the wires to the lock motor or defective from opening and closing the gate or the gate lock motor is defective.

there should be an access panel on the inside of the tailgate that you can remove to find the fallen cable and get your gate open

I had the same problem with 2005 estate it used to open when starting the engine but does not unlock at all. The problem is the the sensor on the glass tailgate handle where the wiper arms is. It will cost around £70 from Jagaur themselves as I have just got one.

I believe you have to open the rear window to open the tailgate??
Tailgate opens right to left [ passenger to driver ] side?
Tailgate handle will not work if window not open - feels like it is disconnected. The "button" releases the window only.
If you open the rear window and the tailgate still will not open. You need to remove the inside tailgate cover to get access to the handle and release switch. You can access the the window release the same way [ just a little harder to do]. You will probably end up breaking the vinyl panel to do this but so will the auto body shop and they will charge you $$$$$ to replace it.