No sadly not. Besides the features you found they also heavily limit the amount of push notifications you can send through their gateway (while simultaneously making it hard to run your own)

Can somebody help me?
I installed Rocket chat for my workplace as a standalone server. Everything has worked perfectly. But I can not receive any notification on my Mobile phone. I surfed on the Internet, and I found out that in order to receive message notification I must register my server in Rocket chat cloud. It is necessary to do that?

If I am self hosting it, why does it say free upto 50 users? Why should I even self host it?

Pure non sense and wasted my time doing all the installation and integration upto some extent.