when do the covert ops take effect ? in the tick they are performed or the next one ?

if i have interpreted your question correctly then its ans is next tick.
Still im not sure what u exactly wanted to ask.

say im attacking this OP and my army is one tick away,if i spread virus or something it will afect my troops that lands on op next tick or only the defenders ?

the spy attack will only affect the units on the op no matter how far is your units from the op



so it it cant affect your units even if u were 1 tick away only nukes does that but not spy attacks