Hi, Givan!
Yes, you can specify the version by running, e.g.:
pip install rasa==2.8.1
pip install rasa-sdk==2.8.1
If you need a step by step instruction how to install rasa you might wanna take a look here:
Windows installtion of Rasa x - #4
or
Rasa X runs with several Errors & Warnings - #7 by vio_lovis
@nik202 walked my through all the steps 
I hope that’s helpfull to you.
Ciao, Vio