Windows process with Untrusted Integrity level

I couldn't find much information about Untrusted integrity level in Windows, and have some questions about it:

1. Is there a place where an untrusted integrity level process can create named objects? (mutexes, events, etc..)
2. Should untrusted integrity level process be able to open an existing named object, that was given a security descriptor in it's creation time with ACE with SYSTEM_MANDATORY_LABEL_NO_WRITE_UP to MandatoryLevelUntrusted? When I try it, it fails with 0xc0000022(access denied), while with MandatoryLevelLow it works great.
3. How do usually untrusted integrity processes communicate with their broker process? (like how does a google chrome tab communicates with the google chrome broker?)