I think you mean crabgrass. Crabgrass can be removed by herbicides that you can spray on but in some areas, spraying some herbicides are illegal. You can just pull them up out the ground and use a shovel for the stubborn ones.
Only if it needs lime. Have someone take a soil test for you to check the pH level. If it reads between 6.5 and 6.7 your fine. If the test reads low...its too acidic and then and only then do you...
I dont know what u mean do u mean dandolion I don't know if I spelled that right well the cotton stuff are like a bigger version of a little yellow flower
Adding lime to your lawn changes its pH value.
Lime is Calcium Oxide also known as Quicklime or Burnt Lime, which is an alkaline. Adding lime effectively reduces the acidity of your lawn.