Can casinos lower the RTP of a slot? Is it possible that in all casinos the same slot will have the same RTP?

We talked about it in an older thread : no they can't directly. BUT some providers can offer their slots with different RTP, and the casino can select the one they want on their platform. That's why some slots have different RTP on different casinos.

But that's not the case for all providers. Some slots will always have the same average RTP.

There you go : http://www.kpvfaw.com/forum/general-gambling-discussion/does-online-casinos-capable-of-changing-slot-games-rtp

Hello. Yes, they can do that. Essentially, there are two possible outcomes. When casinos are running fake games, they can modify the RTP as much as they want. When dealing with real games, only some providers give casinos the ability to change the RTP. 

Why do you ask ? Have you come across something like this ?

Hey, thank you for the appropriate addition and relining of the thread !! It will definitely be helpful ??

There's been a rumor recently that there's a sure-fire betting method with a 93% winning rate, does anyone know about it?

Well, 93% does not very much sound like sure-fire betting to me. Even 95% is not considered a fair chance. You are welcome to explain what's on your mind, please. Perhaps it is just sort of misunderstanding. ??

93% is the lowest probability, but in some cases the winning rate can go up to 99%.

Hmm, what games are we talking about, please? For example, I have never heard that specifically 93% is the lowest probability. I guess concrete details would be handy. ??