Also are there any examples about using these nodes?

- Here are some examples of extrusions:
https://mab.to/XFytegeAo
You'll find them in Common/Tutorials/Extrusion

- Perspective Projection is only for providing a camera matrix for very special shaders used in system compounds. In normal cases you don't have to deal with it at all.

- Placers are for placing a picture within another frame with different size or aspect ratio.
Placer fills the target frame with the picture using a specific Fit Mode, but also can scale, rotate and offset the picture. Offset is relative to the frame size.
Placer Vector does the same, but you specify the Offset and Scale as 2D vectors which is more convenient in some cases.
Placer Area fits the image into a specified rectange (Area) within the target frame. The area is specified in relative coordinates within the frame.
Placer Precise can be used if you want a pixel-precise placing of the picture with a specific alignment to the edges or the centers.

- This video describes all regarding to outputs and channels, including the Channel Out and Video Out modules:
https://youtu.be/uZsB4vNOKtY

- Peekers renders the same preview that the "peeker" windows when you move the mouse over a wire and hold down Ctrl. If you want to continuously monitor one of your output pins, you can wire a Peeker module to it and then wire the Peeker's result to an output or preview panel,  for e.g. with a Channel Out module. Or you can put multiple peeker output together using Placer Precise and send that to the output. You can see an example of this usage in the Touch_Control.xcomp tutorial.

- On the topic of collections please watch this video:
https://youtu.be/XbQcChdIEOo

Regarding the other modules I'll send some examples later.

What about other modules?

-Combiner Block and Combiner Node

-Graph Node and Motion Graph-

-Depth mixer

- You can find a description of Combiner modules here:
https://my.aximmetry.com/forum/postdetails/63-what-is-combiner-node
Please install this to get the example file:
https://mab.to/DKgyq1Jo2

- In the latest version you can find an example of Motion Graph:
[Common]:Tutorials\Misc Samples\Motion_Graph.xcomp

It can be use if you want to define motions in your scene that avoid collision with walls or other objects. Basically you define a series of positions and the allowed paths between them. Then you can send your camera (or an object) from any of the predefined positions to any other, and the system will only use the allowed paths you defines.

The positions are defined by the Graph Node modules, and the allowed paths are defined by the connections between them (the direction of the connections does not matter). Also you have the specify a unique ID for each Graph Node.
Then you add Motion Graph module which itself is a Graph Node, but also the one that controls the motion. By changing its Target ID property you can command the system which Graph Node to move to.

- Depth Mixer can be used to mix together of the outputs of two cameras. The point is that the depth map is taken into consideration when mixing (it determines which parts of one image gets in front of or behind the corresponding part of the other image).