How much does it help when your POI knows/is close to your current PI?

[SupFam]

I posted this on r/gradadmissions yesterday, and also wanted to get some advice here.

Basically I have a Clinical Psych interview scheduled with a POI who knows the PI/mentor I have been working with for the past year. My mentor has spoken very highly of the POI, and recently when the POI reached out to me (interview invite), he told me to make sure I send his regards to [mentor].

First-gen, so I'm on a deserted island in terms of information about apps, and I have so many questions.

1. How common is this? As in, do I have an advantage compared to other applicants? Because I'm going grey with anxiety right now and could really use the confidence boost..

2. Anyone else go through similar situations? If so your advice/results will be forever appreciated.

3. How do I approach discussing the research I've been doing with my previous mentor? When I run it through my head it just feels a bit awkward since he knows my mentor already...

4. I have quite a low GPA (3.04 ovGPA; 3.40 Major GPA, with 1F & 2Ds in major classes, everything else is As) because I had let depression win for a semester (one semester was all it took). To other applicants with low GPAs, how frequently does this come up during interviews? I find it very difficult to talk about that semester. I have a solid >320 GRE score and went to a top 10 undergrad program, if that helps any.

Of course I accept the caveat that this application cycle is pretty screwed, so anything can happen. But I'd appreciate any guidance/comments you may have.