Are all reactions redox reactions?
No.There are other reactions
Redox reaction is a type of chemical reaction, and is the result of electron transfer between chemical species
Examples of non redo reactions
there are precipitation reactions (which don't have electron transfer), e.g. silver cation and chloride anion combining to make silver chloride, a slightly soluble compound. Also barium sulfate will precipitate.
Hydrolysis of polysaccharides and proteins: with the assistance of enzymes, water is use to break up polysaccharides into simple sugars.
There are many more