Is allowed by code in your county to parallel wires to have higher gauge ?

[Yansi]

OT But can't help noticing, those conductors on the top side of the fuses looks quite small for 40A fuses.

Black and grey are swapped after the fuses as well.

Well, even in the lower portion, phases have incorrect sequence: First should be brown, then black, then gray. This different sequence (black-brown-gray) is I think only used in the capital city of Czechia

[SparkyFX]

You can parallel as you wish, as long as each parallel branch is fused/protected separately.

+1 , because if you splice your circuit afterwards anyway, you would avoid not fusing properly in case one connection breaks. This means your distributor panel will have more than one supply, which is unusual and requires some effort to avoid problems (e.g. attention on RCD wiring), but is manageable.

Well, even in the lower portion, phases have incorrect sequence: First should be brown, then black, then gray. This different sequence (black-brown-gray) is I think only used in the capital city of Czechia

For Germany: Utilities can do it as they like, some connect houses in left hand rotating direction, some do right hand. Their terms and conditions apply. The only strict defined color is green/yellow for PE(+N) (unless wrapped with some different color tape to utilize it as something else). It is recommended to not change wiring color within the system so the next guy looking at it won't be confused. The photo shows the interface between two systems, no big deal there, no laws broken.

[pigrew]

You can parallel as you wish, as long as each parallel branch is fused/protected separately.

+1 , because if you splice your circuit afterwards anyway, you would avoid not fusing properly in case one connection breaks. This means your distributor panel will have more than one supply, which is unusual and requires some effort to avoid problems (e.g. attention on RCD wiring), but is manageable.

In USA, the individual conductors do not need individual OCP devices. In fact, this could be designed as a feeder circuit with no need for upstream OCP based on the wire size. However, this this case there would need to be a downstream OCP device (e.g. fuse, circuit breaker, or perhaps even motor resistance). Broadly speaking, we assume that if something goes wrong, there will be a short circuit and that will blow the fuse regardless of the protection's ampacity. This is the same situation as ring circuits where there's insufficient overload protection if the ring becomes broken.

We also install individual RCD on each circuit (or even each outlet) here. I've never seen a RCD unit covering multiple circuits in the USA.

[intabits]

...
Like this (photo)

What's that cable/tube that loops into the cabinet and around its interior perimeter?

[Monkeh]

Fire suppression, at a guess. CO2 or pressurised powder would be my guess.

[rstofer]

As posted above, parallel conductors are allowed for sizes 1/0 and larger which is roughly a 125A conductor.

Think about it, how could I possibly have a 2000A circuit when the largest conductor is 1000 MCM and rated 545A?  OK, 2000A is a little over the top but 1000A still requires parallel conductors.  As 500 MCM is about the largest I want to pull, that 1000A circuit will require 3 conductors in parallel.

A 1000 kVA 480V 3 Phase transformer will have a secondary current of about 1200A and will require 4 parallel 350 MCM conductors per phase.  These are VERY common transformers for industrial applications.