ok, sorry but i need last few questions answered for my dad to stop rejecting the advice.
if all we had was 20lbs of live rock and sand with 50/50 lighting and a power head and a filter, how many water changes would we have to do? how many fish and inverts can we have?
What kind of filter? A filter you would use for freshwater won't be too much help, as essentially the live rock is doing the same thing. When your tank first finishes cycling, I would do a 5G water change and then add your first livestock. After that, Test your water after a week and see what your levels are. You won't have too much of a bioload in there at that point, so you probably will be OK. At this point, figure do a water change every two weeks just so you get into the habit of doing it. Once you start adding fish, continue testing your water weekly or biweekly inorder to make sure your levels are staying OK. Go by this. The 4 fish you listed above are fine, but I would definitely not suggest anymore than that, that's already a bit full. Inverts do not take up a large bioload, so in that aspect you can have quite a few. A good rule of thumb is about 1 CUC member for every 1 gallon of water. Most of that will consist of snails.
what makes corals not survive besides lighting and flow? list the max ppm please
Lots of things. Most of which, you will not have to worry about. Keep your nitrate levels below 20ppm with corals, and keep your phosphates at 0ppm, salinity is usually ideal at around 1.024-1.025. If you get into hard corals eventually, you may to worry about calcium, but with softies, it usually isn't a problem.
if we had everyhting in #1 plus macroalgae, how many water changes would we have to do? how many fish and inverts can we have?
I can't predict how much the macroalgae will help kep your levels down, but regardless of whether you have it or not, the amount of inverts you have would stay the same and the amount of fish at 4.
if we had everything in #3 plus a protein skimmer, same questions.
I would consider a protein skimmer a necessity if you're going to have that many fish.
is there any cheap ways to get rid of phosphates without the use of sumps, skimmers, or algae?
The easiest way to use RO water, although not necessarily cheap.
does live rock get rid of these compounds? ammonia,nitrite,nitrate,phosphate
The main purpose of liverock is to have a place for the good bacteria in your tank to live. This bacteria helps to break down ammonia, nitrite, and natrates in your tank. Although as far as I know, it will do nothing for phosphates (someone agree/disgree on phosphate part?)
what does live sand usually consist of?
True live sand does mainly the same thing as your live rock would. It would contain the bacteria and probably some extra little creatures, like pods.
if live rock is in a bag, is it still alive?
if live rock is in a bag with water, is it still alive?
It depends. The longer the live rock is out of the water, the more that dies off of it. After a certain point, it can't really be considered "live" anymore.
why is an anemone not ideal for a 20 gallon tank?
Most anemones will grow to be about a foot in diameter or larger. That is almost/is bigger than your tank. You also plan on having corals. A large anemone + a small tank + corals = Possible death to the corals. Corals kept too close to an anemone may be stung and killed.
is it true that if you had everything in number 1, you only had to change the water 2 times a month?
Not sure what number one includes 
Again, it depends. But it's certainly possible.
