Hi Guys, I have 8 inch 16GB SAMSUNG GALAXY TAB A and its model is SM-T350. It has Android 6.0.1 version. * I want to delete any file or anything on my Tab more securely. I mean, such deleted ones should not be recovered by any app. What is the free best app for the purpose? * I want to securely erase the contents or free space on a drive. What is the best free app available? .*I have the above-mentioned Tab. It is a new one. What are the settings to be changed for highly security purposes?