Problem:

Query related posts on Toolset post type relationship in custom PHP codes.

Solution:

You can try the Relationship API function toolset_get_related_post(), see our document:

Relevant Documentation:

https://toolset.com/documentation/customizing-sites-using-php/post-relationships-api/#toolset_get_related_post

Problem:
Dynamically displaying to a specific form field required on toolset form

Solution:
You can use "cred_filter_field_before_add_to_form" toolset form hook using which you can set few fields dynamically required.

You can find proposed solution, in this case with the following reply:
https://toolset.com/forums/topic/dynamically-displaying-to-a-specific-form/#post-2210489

Relevant Documentation:
=> https://toolset.com/documentation/programmer-reference/cred-api/#cred_filter_field_before_add_to_form

Problem:

Two questions about the select field customization.

Solution:

It needs custom codes, see detail here:

https://toolset.com/forums/topic/i-have-two-more-requests/#post-2210531

Relevant Documentation:

https://developer.wordpress.org/reference/classes/wp_user_query/

Problem:
center map to different location when address is not in the database

Solution:
Toolset map offers the Map's javascript hook "js_event_wpv_addon_maps_init_map_completed" that you should use to set the default location dynamically.

You can find proposed solution, in this case with the following reply:
https://toolset.com/forums/topic/center-map-to-different-location-when-address-is-not-in-the-database/#post-2209945

Relevant Documentation:
=> https://toolset.com/documentation/programmer-reference/maps/programmatically-change-map-settings/#changing-settings-when-using-google-maps-api