Thanks for the info. My information is older then. As I ever try before, secure erase/shred using some cleaner software (I don't remember which one I try), can render the file in microsd/flashdisk unrecoverable by program such as recuva. If I delete it manually, recuva still can recover the file immediately. I ever accidentally format a wrong 8 GB flashdisk (6 GB data inside) and recover the whole files immediately to full intact as before. If I shred/secure erase (really forgot using which one), the files name become randomized and when try to recover, it will show 0 byte size. Probably this depends on the filesystem too. Both flashdisk and microsd are FAT32. I haven't tried yet with MiXplorer, will try it when I have the chance. To lazy to pull the microsd out just to test this
While in vfat and ext4, as the one used by most android now, there is still no full program can recover those. I wish to know too if there is. Most of the software/app claim they can do it, but simply scamware. But i ever experiment with older android, a qualcomm MSM8610 device, which still support backup full partition thru emmc raw tool. I try to delete something in the internal storage (/sdcard0/), then take full 4 GB raw backup of the file. Then try to recover file directly from the raw img file using raw format recovery, the file is still there!!! So it is only possible to recover the file if we can dump the raw img of the nand flash, which is kinda impossible for new devices (unless we have access to forensic tools). I don't know if shredding the file using MiXplorer can really shred it completely.