Unable to enter new commands in terminal -- stuck with ">"

Solution 1:

You have used the older command substitution syntax `` AKA backticks, with only the first one in the initial PS1. That is, you put one backtick in the primary prompt and have not closed it with another, hence the shell (bash) is continuing to take input on the secondary prompt PS2 (by default >).

In regular cases, just using another backtick to close the substitution would do, but as you have used too many ambiguous commands successively, press Ctrl + C to close the PS2 and get the primary prompt PS1 again.

while we're at it, for any kind of command substitution operation, start using the more robust $() instead of the buggy and deprecated ``.

Example:

$ echo `whoami
> `
foobar

Also, are you seriously trying to do chmod -R 660 /?

Please don't do this, and also don't run any command you don't understand or trust fully.