If iClone 7.4 is installed on your PC, and you are trying to reinstall it then the only solution is to first uninstall and then reinstall. Since I haven't had to do this for quite some time I can't comment on the Plugins, but it is possible that the best - safest - method would to uninstall everything and do a clean install.
It is really a pity that in the 21st century RL can not code an installer that will repair, or even install over, an existing version.
Gerry
System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.