can a redox reaction be like this? 
Q.(4) $Xe{F}_2+P{F}_5\to {\left[XeF\right]}^{+} P{F_6}^{-}$

Dear Student,

Yes, this redox reaction is possible.
 

In this PF₅ is a strong fluoride acceptor, and XeF_2​ is strong flourinating agent. When they react, PF₅ accepts one flourine atom from XeF₂ and gives PF₆^-_​ and XeF⁺. 

In XeF₂ and XeF⁺, XeF₂ is more stable because in XeF⁺ positive charge is showing that it requires one more electron to become stable, and  XeF_​2 does not follow octet rule because it has more than 8 electrons and due to this it behaves like a strong oxidising agent as well.