All one has to do to unlock Call of Duty Mobile's Zombies mode is reach level 5 through playing the rest of the game normally. Once that's done, players are free to play the mode as much as they want while it's available.

Formaldehyde, also known as methanal, is an organic chemical compound and belongs to the aldehyde group of substances. Due to its versatile applicability, it can be found in a large number of different products. It is mainly used as an adhesive and binder in the construction materials and furniture industry.

Adhesive Bonding is the process of joining two surfaces together, usually with the creation of a smooth bond. This may involve the use of glue, epoxy, or one of a wide range of plastic agents which bond either through the evaporation of a solvent or through curing via heat, time, or pressure.