I have a questions, about changing type of giudance and fuse settings when the missile is already lanched. Is it possible to guide 3 missiles at the same time with three different guiding methods (with the real complex).

Yes

Is it possible to switch from one guiding method to another during flight of the missile?

Yes, but the chance of a kill is reduced.
There is a red lamp on the I-32V panel, if it illuminates, you should not change, or your chances of a kill will be marginal.

Can fuse settings be changed during the flight of the missile? (this is for the Volkhov)

No.
Only 4 commands are available: K1,K2,K3,K4