Gonna go against the grain on this one.
Can you learn pickup completely at home, without actually talking to girls? No. You can't delay approaching until you've read or practiced a bunch of stuff at home first. You need to actually get the feedback of how girls react to you and troubleshoot what's going wrong to get better. You need to see how girls around you talk, what they like, how they think, etc. You also need that exposure to uncomfortable situations and how to handle them and remain confident and in control.
Now that that's out of the way - can you practice at home to improve your game. I think
definitely yes.
First of all, you can work on your fundamentals in any social situation. You can practice body language, voice, face, etc at home. Or with family, friends, etc. You can even record yourself. You can get in shape and work on your fashion. You can make a lot of progress here without actually approaching.
For game, you can also work on your verbals. This will really help you if you find yourself stuck not knowing what to say. Write out all of the verbal stuff you commonly use. Make a document, and write out a bunch of openers, responses to questions like "where are you from?" "what do you do?" etc that girls commonly ask you, write out a bunch of ways to tease girls, chase framing, role plays, innuendos, challenges, etc. Ways to reward girls, takeaways, interesting topics to talk about, stories about your life, how you qualify them, how to deep dive and bait the girl to share personal things or try to impress you, deal with tests, sexualize, pull, deal with objections, etc. Whenever you say something to a girl that works, write it down later. Or if you see another guy say/do something charismatic or interesting, write it down. You can even practice opening, responding to things, telling stories in the mirror.
If you really want to take this further, the Game Solved book talks about practicing with tv shows. You pick some drama series with a lot of man-woman scenes, and practice responding to things the characters say. For example, come up with a way to tease a girl, and then deliver it as you would in person. I personally haven't done this.
You should not be getting in your head thinking "what do I say next" when talking to a girl. Ideally, you're not even thinking about being confident or making eye contact, or speaking slowly, and all of that is natural too. Then you can focus your attention on the girl, how she's reacting. etc. And everything else is automatic. Guys who do this stuff are always going to say "you can't just sit at home, you have to actually go out and approach", but that's because they see others make the same mistake over and over of not actually going out and putting in the work. Or letting approach anxiety prevent them from talking to anyone. Most guys never put in the work to actually become good or get results. But imo, you can combine practicing at home with going out (and I think it's possibly even the optimal way to improve)
Also, even when actively pursuing women, certain situations are just rare but when they occur, I have to know what to do.
I'm not really sure if there's that many rare situations that make or break interactions that can't be solved in the moment with general principals. The main exceptions I can think of might be weird logistics situations or weird girls who act abnormal and are hard to read. Maybe certain lmr situations? I wouldn't worry about this until you're good at handling the common things that come up over and over again.
