There are definitely VSCode extensions which ask you to pay for them, like GitLens.

There’s no restriction on distribution. You’re free to distribute the GPL software you got from Red Hat.

They’re under no obligation to ship you other, different software in the future. You’re only entitled to get the source for the binaries they distributed to you. If they never give you the next version, you have no right to its source.

They absolutely can, but RHEL Red Hat will likely stop doing business with them if they find out (and thus stop giving them new versions), hence why they would only be able to do this once.

It doesn’t. The GPL is satisfied as long as they provide you with the source code for the version of RHEL that they distributed to you. But they’re not obligated to continue distributing later versions to you.