The command that displays all environment and shell variables is env. The env command prints a list of the current environment variables, which are variables that are defined for the current shell and are inherited by any child shells or processes. The env command can also be used to run another program in a custom environment without modifying the current one1. The env command is part of the GNU coreutils package and is available on most Linux systems2.
The other commands are not valid or do not display all environment and shell variables. The getargs command does not exist in Linux. The lsenv command is a utility to list information about IBM Power Systems firmware, not environment variables. The ls command lists the files and directories in the current working directory, not environment variables. The lsshell command is a utility to list the available shells on a system, not environment variables.
Reference:
LPI Linux Essentials: 1.4. Using sudo
LPI Linux Administrator: 102.5. Use Debian package management
LPI Linux Engineer: 201.1. Measure and Troubleshoot Resource Usage
LPI Linux Professional Certification Program
https://linuxconfig.org/how-to-set-and-list-environment-variables-on-linux
https://www.digitalocean.com/community/tutorials/how-to-read-and-set-environmental-and-shell-variables-on-linux
https://unix.stackexchange.com/questions/176001/how-can-i-list-all-shell-variables