1) Is it possible to boot into an OS without RAM? If so, then how? 2) I know it's possible to boot Windows OS without hard drive but I don't know how. Anybody got instructions?
I think it's not possible. Without RAM a motherboard won't even boot or give video signal. Google for WinPE on a USB drive.
While I do not believe they were ever sold to the consumer, there was a system which could be tricked into using flash memory as ram, but they were not widely used. Today, as @Mr.X has confirmed, you cannot boot your computer without at least some ram. It is possible to use a computer without a hard drive though, booting directly off of a DVD or USB, only. But you'd need ram for that.
they are looking into replacing hard drives with ram. https://arstechnica.com/information...rd-drives-and-ssds-ramcloud-creators-say-yes/
Yeah, perhaps they're looking for that. Here's the RAMCloud project Arstechnica article linked to: https://ramcloud.stanford.edu/wiki/display/ramcloud/Home