Hi, and welcome to the fetish of the future.
>Usually how many times do you need to listen to a file for it to come to full effect ?
There's no set number. It depends on the file and what your limits are. There isn't really a hard cap on what the "full effect" is, and sometimes the stars will align and you'll get a better effect one time than you do the next. Generally though, 3-5 times with one hypnotist will help you get into their stuff, if they're good. Sometimes it's obvious, like when you experience vertigo while sitting down, or sometimes if it's a good session you're so blank that the question "do you know" is kind of a pointless one.
>How do you know the hypnosis went the way it should have ?
You don't. Honestly don't worry about it. This was (and still sometimes is) the biggest obstacle I had to achieving trance; worry about achieving trance.
The best thing to do is to just sit down, make sure you're comfortable, warm, and aren't going to be disturbed (and won't have to pee, aren't hungry etc.) and then just sit back and listen/watch. Don't worry about what's supposed to happen, just enjoy what DOES happen, whatever that is. Maybe it won't be trance, maybe you won't get that HFO, don't worry about it. Just enjoy it. Tragically, this is probably the best way to go the deepest into trance.
I spent way too many years constantly trying to force myself to trance or whatever while listening and all my best sessions were when I was tired as fuck or out of it on cold meds or whatever and didn't have the energy to worry about how it was going.
>Do you know when you are hypnotized ?
Not always. For this reason, I really like files that prove it to me, like videos that force me to blink/close my eyes, or files that lock my hands in place or whatever before they move on. It's not uncommon for me to think "I'm just watching this video, I don't really feel like I'm goPost too long. Click here to view the full text.