For starts, root is allowed to remove a file even if the writable bits are not set. Also, a common error message due a permission issues is "permission denied". This "Operation not permitted" is totally linked to the inmutable bit set.

The command that will accomplish the goal of avoiding the deletion or modification of files from non-owners is chmod +t /project/access2all. This command will set the sticky bit on the directory
/project/access2all, which is a special permission that restricts file deletion or renaming to only the file owner, directory owner, or root user. This way, even if multiple users have write permission to the directory, they cannot delete or modify each other's files. The other options are not correct commands for accomplishing the goal. The chmod +rws /project/access2all command will set both the SUID and SGID bits on the directory, which are special permissions that allow a program or a directory to run or be accessed with the permissions of its owner or group, respectively. However, this does not prevent file deletion or modification from non- owners. The chmod 2770 /project/access2all command will set only the SGID bit on the directory, which means that any new files or subdirectories created in it will inherit its group ownership. However, this does not prevent file deletion or modification from non-owners. The chmod ugo+rwx
/project/access2all command will grant read, write, and execute permissions to all users (user, group, and others) on the directory, which means that anyone can delete or modify any file in it.

File attributes are preventing file modification, which is causing the error message. The output of lsattr /home/user/data.txt shows that the file has the immutable attribute (i) set, which means that the file cannot be changed, deleted, or renamed. The command setfacl -b /home/user/data.txt tries to remove the ACL from the file, but fails because of the immutable attribute. The administrator needs to remove the immutable attribute first by using the command chattr -i
/home/user/data.txt and then try to remove the ACL again.

Pluggable Authentication Modules allow Linux to work with Google Authenticator and other OTP tools to add two-factor security to your system.
https://www.redhat.com/sysadmin/mfa-linux