Hi Claude

The fuel tap is not original for a Victa Rotomo ,the Victa ones are machined where the fuel hose fits and your
one has a removable brass union and removing your union is a thread that Victa don't have.

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=47908&page=all

No, the main carby body for the brass nut carby is not the same as the ones with a clamp.

Pic of the carby for a brass nut below.
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=34931

Not sure on the starter pulley but it could be very early model 1. It's a little difficult to prove the early drawings are correct.

The model 1 throttle controller pic below.
http://vintagemowers.net/mower_victa_model_1.php

Cheers
Max.