My van makes clicking noise when going uphill & and sometimes the speeds slows right down and makes noise (clicking under vehicle).

yes
the VSS (vehicle speed sensor ) communicates the vehicle speed to the cruise control to allow it to energize or stop when the vehicle speed is too slow
it does that through the ECM unit

That's a relay you hear clicking, you may have a short or a bad relay.

im going to say an almost dead battery .the hum you hear might be the fuel pump.you never heard it before because the van normaly starts .so boost your van if it starts you may have to replace the altenator the guages, no worries many cars do that .thats a code needing erased and if you disconnect the battery that may go away.

I had a Ford Winstar van that had this problem. There is an acceleration switch near the firewall on the passenger side that needs replacing. Unless you're very good under the hood, see a mechanic as it's a totall B**ch to get to the darn thing!

well at least you could honestly say "officer I wasnt speeding, actually I wasn't moving" lol
but on a more serious note, the problem mostlikely stems from the vehicle speed sensor which should be located on a front wheel, usually the left front but sometimes the right front. and they can sometimes be a pain to get to since they like to hide under the rotor right next to the CV shaft. this advice is based on the understanding that with the cruse control on the vehicle can't remain at a constant speed on flat ground.

Thank you for getting back to me. I would like you to check your transmission fluid. start the engine and let it warm up at idle speed for about 15 min and check the fluid. It sounds like you do not have enough in it, there for the whining noise with increase of speed since your transmission is speeding up with the rate of your vehicle. If this does not help and the problem persist please let me know. If the noise you were hearing was coming from the u joints of the vehicle it would not make a whining noise with increase of speed. The u joints will only make a noise when they are going bad when the vehicle is shifted into any gear from the shifter( EX: park to drive, park to reverse ECT.)

the battery can be dead enough that a jump wont help

Well if the motor is making noise the wheel could be broken or possibly gotten something in the cage where the wheel is. If the speeds of the motor dont work on any setting but high the resistor is out

have they checked front c.v. joints, as far as knocking noise it could be several things.

well usually this called detonation, also known as pinging. In most cars, this is caused by advanced timing or incorrect fuel octane. In your case, timing cannot be changed so going to a higher octane fuel will help. If you can find some, get some combustion chamber cleaner and add it to your gas. Sometimes, carbon deposits can cause pre-ignition/detonation