will they mate? if so, what do water condtions have to be? i have a 35 gallon

While these two are in the same genus, they are unlikely to breed because the male's gonopodium is too small and short to mate with a female molly. Their parts just don't really fit together.

However if you wanted to breed livebearers in general, make sure your waste levels are low and the temperature is around 78, and they will normally breed like crazy. Mollies and other livebearers enjoy the addition of aquarium salt as well.

Not likely guppies are agressive fish and tend to kill other fish. Atleast all my guppies try to kill other fish (thats why Grumpy and L.Pez have different bowls)