Is it possible to install multiple distro on a device ?

Yes, it is possible, every distro are installed to /data/data/com.termux/files/home with their name:

For example:

Ubuntu is /data/data/com.termux/files/home/ubuntu-fs Kali is /data/data/com.termux/files/home/kali-fs Fedora is /data/data/com.termux/files/home/fedora-fs

You could find out the directory by running ls command after starting Termux.