You did not written your phone'a type, but if you have D750/K750/W800 and similar
1. you can do it with FAR. Go to flash directory and copy from memory to your pc RAW, starting address 44020000, lenght 13E0000
2. you can flash it using XS++ software
3. if you flash the main FW with the same version as your FS, you not need to flash FS
4. no, if you patch the phone or flash main FW, you won't loose anything. It's like using SEUS..