Speedometer jumps I have a 1995 Subaru Legacy 240T and recently i have noticed the speedometer(km/h) jumps even when i am slowing down

You can set it to do that or not do it. It's explained in your owners manual.

you need to make sure that all connections from each unit are attached properly and free of corrosion.
also it is not unheard of to get a bad part fresh out of the box. so you may want to check that as an option too.

the speedometer/odometer problem sounds like the vehicle speed sensor, which is ususally found on your front wheels, the stalling out sounds like an unrelated problem, but i couldnt tell you where to start for that one

Check your fuse under dash. Then if that is not it, there is a speed sensor on transmission that may be your problem. If it is bad or disconnected it will cause a variety of problems. Good luck and have a great day.

check exhaust for blockage(cat) might be bad.

It's probably your speedo head, the gauge itself. I put several used ones in our car to no avail. When I finally went to the dealer they needed to know my cars serial numbers then sold me a gauge that matched my car. Sounds goofy but it worked! I didled with this problem for over a year on and off before that.

throttle cable

sounds like the bands need adjusting in the trasmission

A solenoid needs so much power to kick in.  I think your battery is getting old and not at full capacity.  Hove it check and replace if needed.

replace the relay.

Robert