How to find out the names of RedHat dependency packages and download them in bulk in rpm format?

Question

Red Hat Enterprise Linux

The server has RHEL6. From the server to the Internet and outside there is no way out (and never will be). No way.
You need to install some packages (devtoolset, python, nodejs).
Rpm packages can be installed manually. There are no problems with sending packages to the server.
BUT! You start installing a transferred package (for example, devtoolset), and it has dependencies - 4 other packages, and those four need more packages, etc.
In general, it turns out such a dependency tree, pieces in 200 packages ...
How can I find out the entire list of dependencies without running through the entire "dependency tree" with pens?
To download packages and transfer them to the server. How to pump them out "en masse"?
Maybe there are some other ways (for example, install CentOS6 on another server with an Internet connection, download packages via terminal commands and transfer the code to RHEL6)?