Welcome to AA!!
Live Rock means you have living bacteria colonies in and on the rock. The rock itself is not "alive".
The white stuff could be a lot of different things. If you can get a pic of exactly what you are talking about we can help you figure it out.
Cured live rock means it has been in SW
for a period of time and has sufficient colonies of bacteria living on it. Uncured rock means it has dead or dieing life on it and will cause a cycle or ammonia spike in a system. The process of curing the rock is just allowing the dead or dieing life decay and be consumed by bacteria as the bacteria colony grows.
Your PH is low but that comes with a new system. Have your LFS
check your other parameters but I encourage you to get the kits and test yourself. You don't have to buy them all at once as they can be pricey. I would start with PH, Nitrite, Ammonia, and Nitrate. From there you can add calcium, phosphate, magnesium and a host of others as your system demands them.
Your rock will color up over time and that comes from lighting, flow and good water conditions. The purple you see on rock is coraline algae and it grows from the calcium in the SW
. Over time you will see it growing on the rock, glass and even your powerheads.
Hope that has helped you out.