So file permissions are divided into three parts, for example: -rwxr--r-xI understand that the order is the following: owner, group, othersBut, can root do anything with the file even if there is no access granted by user to 'others' ? 
File permissions for root
files;root;access control
Yes. The kernel ignores permission modes when the user is the superuser, except for execute permission when trying to run a program. See Unix execute permission can be easily bypassed. Is it superfluous, or what's the intention behind it?for more details on why the execute mode is still obeyed.