Will Questions

 Is a do not resuscitate "DNR" the same thing as what is in your HCPOA/Living Will?

 No, a DNR applies to being resuscitated in a specific case. It is usually the case that you are presented with a DNR if you are entering the hospital and the hospital is giving you the option that if your heart stops whether or not you wish for them to restart it.  This is offered usually in higher risk surgeries and typically the DNR is only effective for one procedure, but you should always check with your healthcare provider. A living will only applies in three situations and all three situations are end-of-life: 1. wasting illness (like cancer), 2. mental illness leading to demise (dementia is causing organs to shut down), or 3. you are in a vegetative state and there is a high-degree of medical certainty that you are not going to recover.

When does my Power of Attorney "POA" go into effect? 

As a general rule, your POA is immediately effective. The only way to avoid it going into effect immediately is to add springing language. Make sure when you are speaking with your attorney that you discuss the difference and what choice is the most appropriate for your situation.

I want to donate my body.  If you donate your body, do you get your body back?  What about if you donate your organs?  Do you get your body back?

That would depend on to which "science" program your body is donated to but it is incredibly unusual for an organization to piece out a body.