a) Categories listed in left Panel is not coming in alphabetical order.
b) Searching for Existing Files". Is it possible to have a box with options in Tools-> options so that we can enter the max no of files to be searched. Currently limited by software to 500.
Categories aren't implemented by a plugin, they are part of Azureus itself. Tags are a replacement for categories but there are still some cases (in old plugins for example) where categories are still used. As part of 'migration' categories have been modeled as a type of tag. Please just ignore them and don't use them - one day they will be removed, or at least hidden by default.