Property name (guid / namespace) scope and rules for custom single value extended properties

Hello,

I need to add a custom extended property on events and intend to use a "named" "single-value extended properties" as explained in extended properties overview , with a property identifiers in the 0x8000-0xfffe range as in the example :

"{type} {guid} Name {name}" "String {8ECCC264-6880-4EBE-992F-8888D2EEAA1D} Name TestProperty" Identifies a property by the namespace (the GUID) it belongs to, and a string name.

The MAPI Property Identifier Overview states that :

Beyond 0x8000 is the range for what is known as named properties, or properties that include a 128-bit globally unique identifier (GUID) and either a Unicode character string or 32-bit numeric value. Clients can use named properties to customize their property set

As a new developper in Office365 environment, the GUID generation and its scope in office365 are not quite clear to me :

1. Does it means that we are free to use any 128-bit GUID/Namespace in the 0x8000 range to set a custom named property ?
2. What is the scope of the GUID/namespace in that context ? Is it limited to my graph client application or shared with others ?
3. Even if the conflict risk looks weak, is there a method to check/generate my GUID ? or to get some GUIDs already used somewhere that could collide with the one i am using ?

Regards,