Hi.
No particular reason to uninstall an ns2 version. Unless it s corrupt.
You can have as many ns-allinone as you want, installed at the same time :
How to remove unwanted :
$ rm -rf ns-allinone-2.35/ && sudo rm -f /usr/local/bin/ns
Reason for /usr/local/bin/{ns, ns235-orig, ns235-lte, ns231-crcn, ns234-anthocnet} :
... If you have several 'ns', they better have different file names.
See my list `usr.local.bin-29Sep19.txt´