Bike modification/alteration Base on the photos as shown, is it possible to apply the following modification/s and/or alteration/s:

a. replacement of wheels from 20" rear-18" front to 16" both rear and front.

b. installation of disc brake since the bike frame and fork is designed for rim brakes.

c. replacement of the "uncommon" rear suspension to a more common suspension easily found in shops.

The bike is an aluminum alloy.
a. replacement of wheels from 20" rear-18" front to 16" both rear and front.


In principle. However, as pointed out in a comment to the other version of this question, you'll have problems with your brakes because both they and the axles are in fixed positions and the brakes need to be agains the wheel rims. Also, changing the wheel size as you suggest that would lower the back of the bike by 2" and the front by 1", and I'd be worried about the increased risk of the pedals striking the ground while cornering. Why would you want to do this, anyway?


  b. installation of disc brake since the bike frame and fork is designed for rim brakes.


If you have to ask, the answer is almost certainly "no". Fitting disc brakes would require attaching the mounts to the forks and rear frame and, if that's even possible, it needs to be done very well, since disc brakes generate huge forces. Indeed, the forks and frame themselves might not even be strong enough to cope with those forces.


  c. replacement of the "uncommon" rear suspension to a more common suspension easily found in shops.


I don't even understand why you'd want to do that. Rear suspension is an integral part of any bike design; "replacing" it would involve completely re-engineering the frame.

If you want to tinker with a bike, it's best to get one with a standard diamond frame. Folding bikes are unique designs and every aspect of them is designed around the need to fold. That means they tend to use weird geometries and heavily custom components that are unique to that particular design.