You do not explain how your hiking app will work @Kadour_Aissa . Because I do not know your intentions, it difficult to respond to your questions. Are you just trying to keep track of a number of hikers or share everyone's location. What is your app supposed to do?
add this application with the social distancing application for the possible sharing of other hikers
Yes, it is possible to merge the features of National Park Tutorial (Markers) updated with the features of the social distancing tutorial. If it is your intention to share locations, the Social Distancing ... a CloudDB / Location Marker Tutorial might be a better example as it uses a shareable database. What you do depends on what your app is supposed to do.
number of hikers is different on each outing
Do not confuse Run time Markers with Design time Markers. This example uses Run time Markers; it spawns additional markers as needed depending on the number of locations in your csv file. Handle the number of hikers by using Run time Markers or using hidden Design time markers. If the number of hikers is not large, I would use only Design time Markers and make them visible or hidden depending on requirements.
I don't need name or distance except marker for security
Only include the features you require in your app. The tutorial has features that are not appropriate for everyone's app. An ID associated with each Marker is useful but not necessary.
Is it possible to add several markers in case there are a lot of hikers or it is necessary to program codes for each person
The National Park app uses Run time Markers. Run time Markers are difficult to code for various reasons. It is often better and easier to provide more Design time Markers than your app needs instead of using Run time Markers. Hide the Design time Markers in the app you are building until you have to have another (Marker1.Visible = false to hide; = true to display).