By default tridion enables a new RTF button in all RTF fields under Edit Formatting Features. I need to disable my newly added RTF button in all fields and should enable it only in one RTF field. Is there a way to achieve this functionality.
As Frank's comment suggests, if you want an automated process to update multiple schemas at once you are going to want to use the Core Service. His link shows a similar scenario.
In your case you could simply retrieve a list of all schemas as discussed here, then follow my solution in Frank's link to retrieve the SchemaData XSD for each schema. Once you have this, some string/XML manipulation would let you add the "DisallowedActions" element needed to turn off your feature.