My vw velociti, cuts or interrupts power when i indicate and when the fan goes on and sometimes when i brake and it sometimes resets stuff on the cluster like the clock and the trip meter. i bought a bosch regulator and it stopped for about 2000 ks then it just started again this morning.

Check the Freon levels while the car is running with the A/C on. It sounds like its low which happens from age.

Of you seen any brake fluid when changing pads the the leak needs to be addressed and brakes need to be bled out of any possible air in system. If this was a problem before then you have a bad master cylinder or brake booster.

every time you disconnect the battery you cause a program corruption in the CPU. Fix the battery drain ( have a load test done on the battery as it may have a dead cell) Then use a code reader to reset the CPU and go from there.

Well, your description sounds like disk brake issue(s). There is a wear indicator that acts exactly like what you describe, if the pads are worn, they need replacement.
If pads are good, you may need "mechanic in a can" stuff that goes between the METAL parts of the pad and it's mounting. Look for rust, as that is a likely area. This goop does not go on surfaces that need to move against one another, those areas need high temperature grease, a small amount.

abs sensor blinking is usually cause by a bad wheel speed sensor or vehicle speed sensor. not too sure what going up hill is doing. sometimes that can move brake fluid around if its low and will detect low brake fluid, but you brake like would also come on with the abs sensor. check and fill brake fluid to fix that. to fix a sensor you need to bring the sensor readings up on a vw scan tool to see which one is cutting out. should take to vw shop for scan tool. they might charge you .5-1 hour diag time but its better then the hassel and expense of parts replacing. finally if they find nothing wrong with the speed sensors going up hill, then its probably the abs unit. check those in that order and you'll find it.

Classic 109 relay failure.

Relay is for the Glow Plug system.

This relay provides the power to all of a TDI's engine-based electronics.

If the glow plug light comes on intermittently by itself, check your brake lights too.

A burned-out bulb will cause the glow plug indicator light to come on. Sometimes flashing is caused by a bad Brake Lamp Switch on the Brake Pedal. It was updated for free by VW .

If you can see it under the knee panel, the Brake Lamp Switch body should be Metallic Green....if it is Purple or Black it need updated.

Check around in that trunk for loose wires. Especially a grounding wire at the taillights. Sometimes in our hurry to shove stuff in the trunk it's possible to disconnect, or cut a wire... If you've got the 'cyclops" light working on the hatch, then there's power back there, just look around and I'm sure you locate a loose or damaged wire... trace them back from the taillights and look close for cuts, frays, damage, loose connection..

first clean throttle body out with carb cleaner and some clean cloth , if the throttle flap is dirty the car will stall

Sounds like another VW made in Mexico.
Have the ECU checked for shorts, it sounds like it needs replacement.
Also check your vacuum hoses for leaks.

These old models of Fox's are just that old. I have been told that the engine light goes on due to the lack of oil pressure in the car. The valves apparently get worn out and create a lower pressure that the oil will pass through them...therefore sometimes this registers as an engine light going off every now and again. However, my mechanic has told me that these old german cars are like tanks and can run on and on and on....on lesser than normal oil pressure in the engine. Keep it well maintained and watch for any abnormal or steady warning lights. My mechanic says don't take the car any farther away than I would chance a tow ride back. If that is a hint or what! Lol.