The major product formed in the following reaction is

Concept:

Cbz(carboxy benzyl)-Protecting group:

• It is used to protect amine group. 
• It is synthesized by the reaction of benzyl chloroformate (BnOCOCl) with any weak base.
• Cbz makes -NH₂ group less nucleophilic as the loan pair electrons present on the amine group are in conjugation with the carbonyl group.
• Example
  
• Deprotection of amine group or removal of Cbz-group occurs with the help of strong acid like HBr/AcOH or in the presence of H₂/Pd.
• Example:

t-butyl ester: (CO₂t-Bu)

• When carboxylic acids react with isobutene in presence of acid, it gives t-butyl ester.
• Example:  
  
• It is used in the protection of carboxylic acid group(-COOH).
• t-Bu ester being a bulky one doesn't favour nucleophilic attack to which it doesn't undergo base hydrolysis rather they prefer acid hydrolysis.
• Example:

Explanation:

The mechanism of the reaction as follows:

Conclusion:

Therefore the correct answer is option (4).