Please explain about the red dots in the below picture
The red dots definitely have the same shape and size as the showing pads for TP4003 and TP4003. The ones that are red are covered with the solder mask and thus the reason that they appear in the red color!!

It is likely that the original PC board artwork designer placed test points on every net of the board and then later modified the solder mask to cover those not needed on finished assemblies. There are several pairs of covered test point pads in the lower right corner of the picture that even have silk screen indicators as test points that support this guess.

Some bare board manufacturing facilities may make use of all these test points to electrically check a raw, in process, board for shorts before committing it to later stages of fabrication. In the early manufacturing stages these pads would not yet be covered with the solder mask. This can lower overall fallout at the finished board test station, especially for cases where there are a lot of layers involved in the board stackup. Such in process testing may also apply for testing buried via layers as well.