I installed the plug-ins ‘Locate Points Along Lines’ and ‘LRS’ (Linear referencing System) and I followed the video [Linear referencing in QGIS 3 | burdGIS] (https://www.youtube.com/watch?v=meC3AfTOtps).
I used the first plug-in to calibrate the road-polyline layer
Then I used the Calibrate tab of the LRS, for the previously created temporary layer, to create the Routes temporary layer
I used the Measures tab of the LRS to locate my points (point layer) in sequence along the Routs layer I created before
I continued with the Step-3 of @Taras from my initial Question [Projecting polygons into polyline]Projecting polygons into polyline.
a) I used 'Points to path' and for ‘Order field’ I used the ‘measure’ field created at the previous step, while for ‘Group field’ I used the ‘route’.
b) I had also to ‘Explode’ the lines created (as in [Splitting all lines in layer at vertices using QGIS?] Splitting all lines in layer at vertices using QGIS?).
c) I added the length of the lines ([Calculating Line Lengths and Statistics (QGIS3)] https://www.qgistutorials.com/en/docs/3/calculating_line_lengths.html).
d) Then I was able to select those lines longer than my requirement (35.68m in my case) and to delete them (when at Toggle Editing) together with other unsuitable lines created.
e) Afterwards, I ‘Dissolve’ these lines into polyline segments in order to create the proper Buffers at the next step.
Then I was able to continue with the Step-4 of @Taras from my initial Question ([Projecting polygons into polyline]Projecting polygons into polyline) and to create the 'Buffer' by using 3.5m for ‘Distance’, Flat for ‘End cap style’, and Round for ‘Join style’ in my case.
Finally I applied ‘Intersection’ between the original polyline-roads layer and the Buffer layer from the previous step to get the polyline segments of my interest.
I had also to apply ‘Multipart to Singleparts…’ to have the segments as individual features at the layer’s Attributes.