Attempting to reverse-calculate a password is called

Cracking. Hope this helps. :)

1. The repeating units in a fatty acid are just carbon atoms. They usually have two hydrogens attached, but can have one (in unsaturated fats) or three (at the end of the chain). This is simpler than nucleic acids and proteins. 

2. Fatty acids are used to make phospholipids, which make up most of the mass of a cell membrane. The fatty acid portion of a phospholipid is very hydrophobic (does not mix with water).