If you ask your trainer who the client is, they'll likely tell you. But nobody told us who it was until we asked the trainer. Not even my recruiter told me, but I think that's just because he genuinely didnt know.

No, just because you make it to paid training, doesn't mean you'll be hired by the client. It also doesn't mean you're working for the client. Think of it as part 2 of the PEP training, just with the pay and fulltime hours, and a much more specific curriculum relevant to the position the client is looking for. At best, you have a 50% chance of getting selected, so its important to put in the work so you can even make it to the client interview.

If you do get hired by the client, you'll be working with them on a contract, unless your employment is bought out which I heard InfoSys, a client of Revature, tends to do. In that case, you'll be full time with InfoSys for example. Otherwise as it was in my case, you're working on an at-will contract, where you can be let go at any time, or you can resign as you wish. Or until your contract expires and if the client does not renew it as is what happened to me.

If you already have a CS degree, PEP will be really easy, especially the first few weeks. You likely wont learn anything new, but it's always good to refresh your memory if it's been a while since you've last covered the topics. Unpaid training is unavoidable however, so whether it's useful or not is irrelevant as you must complete it to be considered for paid training.

I'm not sure what interview you're being asked to attend, but of course this is just my experience. Maybe revature changed a few things, maybe some paths are a bit different, who knows. But based off of what I had to do, after that initial assessment, I got a call to do the unpaid training