citrate result is positive in case of pseudomonas aeroginosa. slant and butt both will be positive

The test indicates if an organism utilizes Citrate as it's only source of Carbon. Positive results will show growth on slant as well as changing the medium from green to blue (ph indicator)

yes you can use either trisodium citrate or sodium citrate

Citrate is the salt, an ester of citric acid, and the polyatomic anion that is found in solution. The ester can be triethyl citrate and the salt can be a trisodium citrate.

Citrate Permease is an enzyme that is responsible for transporting citrate inside the cell. Some bacteria have this enzyme while others do not. You can test for the presence of citrate permease by performing a Simmon's Citrate biochemical test.