fix an issue with my android app

I have 3 APKs : [login to view URL] manager with functions like delete files and folders, share files, rename files and folder, select all items,display properties of selected file or folder,create new folder (all functions in internal storage) and sd card with only read functions like share files, display properties of selected file and folder, select all items 2. Now I hired a developer who added two new features- a. display previous screen on back press b. move files from one folder to another inside internal storage. But he modified code in such a way that many previous functions stopped working including share files, display properties. 3. I hired another developer who added some more new features- [login to view URL] write access for sd card [login to view URL] files faster using asynctask but the features mentioned in 2 were not working. Also create folder wasn't working anymore too My requirments : Combine all this in one app which has following functions Internal storage - delete multiple files and folders,share files, rename files and folders, select all items,move and copy files from one folder to another, display properties of selected file or folder, display previous screen on back press, load files using asynctask, create new folder SD card - share files, display properties of selected files and folder, select all items, delete multiple files, grant access for write operations in sd card NOTE 1 : I do not want to add any new features . All features are in one of the 3 APKs. Its just that you need to combine 3 into 1. NOTE 2: The project is being created using API 17. The API level of the project should not be changed . App should be able to run on all devices with API 17 or above