Connexion is the original and variant spelling of "connection", common until at least the 19th century, and still occasionally used in British English (it was the house style of The Times of London as recently as the 1980s). It is derived from the Latin connexio, hence the spelling, unlike most words ending in "-ction" which are derived from Latin words ending in "-ctio" (e.g. "protection" from protectio).
1) How do we pronounce the above word, connexion?
Like connection, its successor can be pronounced as con-nek-shun, how can we pronounce connexion? perhaps con-neg-zhun? And if it is the same as connection, then why so? the spelling and origins are different.
2) How do we pronounce its verb, connex? (But is connex even the verb of connexion?)
Like connection's connect can be pronounced as con-nekt, how can we pronounce connex? can it be con-neks? or simply con-nekt, but there is no sound of k or t in the spelling.
Lastly, as British English user, is it acceptable to use this word as a substitute to connection in formal English or is it completely taken over by connection?