1A: mash - hold mixture of malted (sprouted) grain and water at specific temperatures to permit specific enzymes to convert starch to sugar.
1B: wash - well, other than cleaning up, presumably (not a term normally used in barley brewing - "lauter" is the terminology there) presumably for sugary product that's not converted from starch, "washing" it out of the "bagasse" (cane sugar term - plant stalk waste) - very similar in concept to lautering, I'd guess, though I thought sorghum was mostly just squeezed out in a mill and the syrup collected, in which case you would not be bothering with this step. But perhaps you lack the mill and are starting from plant parts?
1C: Boil - boiling. What's to know? Add heat, get steam.
2: No rolling boil, no hop bitterness. Essential to what we think of as "beer". I suspect there is also "hot break" material in sourghum that could stand to be removed, as well (it does not come from the hops - we usually wait for the hot break before even adding the hops - it's from proteins in the barley malt).
3: Any home-brew store (online or local), or you can buy two for $3 that think they are paint strainers at any well-stocked hardware store - get the 5-gallon size - wash well and boil in plain water a few times before use in beer.