What is Bio Film in a bong? And can an additive like RezBlock prevent this?

Biofilm is created by micro organisms.  Changing your water is what prevents this.  Rezblock stops resin from sticking to the glass, but does is not a disinfectant, and if it was, it would not probably be good to breathe in as you will inhale small bits of any additive, it why we say keep your rig clean!

Is cranberry juice a safe substitute for water to fight resin build up?

We feel no matter what you do when combusting you will have a lot of buildups.  The best way to solve this is to move to vape like the Silver Surfer or to rinse your water pipe each night.  You can put a lot of things in your bong to enhance the experience, but nothing is better than when it is clean, filled with whatever you want.

Is cranberry juice a safe substitute for water to fight resin build up?
Can you add lemon juice to your bong water to fight resin build up?

Why does dab water look milky after a lot of use?

This is probably because of the microorganisms growing in the water.  This could be also that the oils are dissolving into the water.  Over time water and oil can mix.  See this article.

Either way we suggest to change your water out daily, if not each night and let dry overnight.

Do people need to use different temperatures for different consistencies of concentrates? If so what kind of different temperatures?

In reality, each degree will release a different cannabinoid, terpene, or flavinoid.  But, if you are dabbing at about 430-450, you will get all the goodness.  Going less will leave some goodness behind as the highest temperature to let the last cannabinoid go is 428.  Learn more at Elev8 Presents in the Cannabinoid section.

While this is all true info, we have found that diamonds for whatever reason seem to need a higher temperature.  This makes no logic as the diamond should not be required to get that high.  But it does.

Can soap and water be used to fully clean my Glass?

If the water is hot, it will for sure help to get the gunk out.  The soap will also help to release the gunk.  We trust Dawn dish soap as a great soap to try out.

This will for sure get your glass clean if you clean on a regular basis.  If your glass is filthy you will need to upgrade to a more harsh chemical like alcohol or a formula 420 product.