Replacing ABS sensor (front right}.

1 HTF do you pull it out?

2 How do you squeeze both buttons on the plug at the other end?

3 Two lower clips have dissolved. Are there part numbers and are they still available?

1. With a pair of pliers, pipe pliers seem to work best. If that doesn't work, you'll need to drill it out.
2. Squeeze with your fingers and give it a wiggle while pulling.
3. Which ones?

Having replaced ABS sensors many times herewith my most successful methods:

1. The ABS sensor has a slight ridge/lip around its circumference at the top just below the cable entry. You can get a flat ended screwdriver under this lip on each side and lever the sensor upwards using the hub 'sleeve' as the fulcrum. Once you have a decent gap twixt hub and sensor then locate a screwdriver flat end under the lip and pointing up at an angle and gently tap the sensor out. If you use pipe grips or similar too heavily it distorts the sensor body which only serves to jam the thing more tightly in the housing. Always use a new clean cage and plenty of silicon grease when installing a new sensor.

2. What buttons? Its just an interference fit on mine but the internal lug prevents the connector being twisted to help removal (there is a groove in the ABS sensor male plug end that lines up with the lug in the female socket to line up the two electrical pins). Therefore it requires a very thin flat bladed screwdriver to (very) carefully lever male plug out of the female socket slightly and once it has started to move it then requires an amount of manual BF&I* to completely separate the connector.

3. The clips on the hub and bodywork that the cable clips into 'dissolved' on mine years ago. I have a plan to make up some more when I have the inclination but they are not strictly necessary - the ABS sensor cable can be loosely cable/zip tied to follow the route of the hydraulic brake pipes - just make sure the route is correct with enough 'slack' so the suspension can operate without straining the cables and the front wheels can turn lock to lock without stressing the cable. BTW, I have rarely found the rubber 'grommets' on the sensor cable to be in the correct position and these often required their position to be adjusted to fit into the clips with the correct routing and radii - so don't use them as a guide as to the correct placement of the cable.

*Brute force and ignorance.

I made up a special tool to get the sensor moving which works well. As Garvin said there is a ridge around the circumference of the sensor at the top. I ground down an old cycle cone spanner that just fits under the ridge. It spreads the load out evenly around the circumference. It is thin and made of hard steel. There is enough space to get a small ball joint forked wedge underneath the spanner. A few taps with a hammer on the wedge and it starts to move. Problem with using a big screwdriver as a lever is it acts in one area and the amount of force used damages the sensor. A normal spanner will also not fit hence the reason for using a thin cycle cone spanner. It is probably 1/8 to 3/16" thick.
A bit of preparation is needed first. I wire brushed around the sensor with a small stainless steel wire brush. Then soak it for a few hours with proper penetrating fluid.
The sensor and inside the hole need polishing with emery paper and wire wool. I used silicone grease for reassembly. It is more water proof.

Perhaps I wasn’t clear in my previous post. I use two screwdrivers simultaneously, one on each side of the sensor to get it moving straight and not binding. I find that once it has started to move then it will come out relatively easy with some light tapping under the lip. I did have one many years ago that would not budge no matter what method of persuasion was used. Yes, that one had to be drilled out! However, by using copious amounts of silicone grease and shiny new cages on installation I have not had one ever corrode in place since. It must be silicone grease to be sufficiently water repellent/insoluble.