Ubuntu Security :: User (in Jail) With Very Limited Permissions

I want to have an account (beta user), on which:I can use the Internet and other programs without administrative rights without the right to install programs with a kind of sandbox for everything that is connected to the Internet, which means: everything that is associated with the web browser's processes and files that I save to hard disk I want to be separated from the rest of the system, so that whatever can catch up on this account will be locked in it, for example any (if at all) possible malicious scripts from Internet or whatever may be dangerous now or invented in the future. Sometimes, for example, I save the web page to disk with all it content.

And in case someone cracked into this account I want make it in that way that he could not do any tricks to read or change passwords, or make any other changes to the system. The best would be if a password for that user might serve only to log in without having any other powers, and I would give that user an automatic login. For now I created a beta user without administrative rights. I understand that the limiting rights of the user are associated with limiting rights to their home directory. There are also groups, and a user may be included or excluded. I excluded that user from admin group but I don't know what else I can limit and how. When I give chmod 0644 for /home of this user he cannot run Firefox. When I give him 0740 he can run applications, so I assume the x attribute must be preserved.

This is a user without sudo rights, so when I type sudo apt-get update a message shows up correctly that this user doesn't belong to the sudoers group. But still it's not what I wanted. When the user runs Gufw and wants to change the settings to disable the firewall, a message shows up asking to type in a password of alpha user = primary user, which is that belonging to the sudoers group, the first / main user that I created during system installation. I wish that there was only the message that the beta user has no power to change anything, which means even completely remove the possibility of asking for sudo.

In addition, I wish that this beta couldn't be able to change the permissions to its home directory, or go to see what is above. Because so far beta can change the file permissions for its /home, even without a sudo password. How can I do it? Do I need to create a kind of chroot jail for this user? I would like any changes to that user account could be made only after the user log off from beta account, and log in on alfa account and that beta could run only programs that ware installed by alpha. And that beta could read and write, but alfa could also read and write or remove, alter files on beta account. Basically, alfa account should be superior to beta account. Can do that?