We should take this to the Chess thread, but I either read or watched a video on YT about it years ago whereby someone recounted a comment made my one of Kasparov's cohorts during a World Title bid... that he was 52 deep there or thereabouts. I remember the number because I thought it was mind-blowing. Am sure Kasparov would deny it in his own inimitable way, but he has produced long videos on sicilians and knocks off 25-30 move analyses in his sleep, so it's quite possible.
Don't totally agree with your second point... it's perfectly possible to see 5 moves deep, even in very tricky positions, and I consider myself to be an amateur enthusiast.
Yeah we should, so my last post here for continuity and then the mods can move it there if needed and we can continue there but I think you're exaggerating a fair bit here mate. I'm an amateur enthusiast as well and I've been to a few tournaments, so by a combination of that experience and online education, I think analysis is different & predicting the variation is extremely different.
You can easily analyze plenty of variations outside of a game for any number of moves, but when you're on a game and when it's actually playing out, trying to read more than 10 moves ahead is going to be a bit of a waste and GMs know that. Of course, when talking about opening variations, there are plenty of variations possible and GMs know them by heart for about 10-15 moves of multiple variations of same opening, say Sicilian or English or Queen's Gambit, that's standard theory. But they're not calculating anything there. They just have openings and variations that work for them and know the theory by heart.
But it's different when you're into middle game. I've gone through some seminars by GMs and the common advice I get is to find out 3-4 candidate moves that you can play at a given position (solid moves), work out 4-5 moves from there for each candidate move and calculate which of those moves yield best result. When calculating the moves forward, you assume the best response from your opponent of course, but if you do a bit of miscalculation & the opponent's response was outside your plan, your plan goes for a toss. Of course, if you're consistently choosing good candidate moves, then you're a solid player. If you can work out 50 moves ahead or even 25 moves ahead from middle game, then you have the game figured out and even the strongest of machines haven't got the game figured out. They lose games occasionally to human players.
It's possible for an ordinary player to see 4-5 moves deep, every now and then in a game, but not consistently and not the better candidate moves, if you get what I'm saying. That's why he/she is an ordinary player. The difference there between them and GMs, even basic GMs, not Super GMs is not the number of moves ahead they see into, but the quality of moves that they see consistently for every response from the opponent. They see the same candidate moves at each position in the game as an FM or even lesser rated player does, but they consistently choose the best candidate move for every position they have in the game.