निम्नलिखित में से कौन सी रासायनिक अभिक्रिया हैलोजन विनिमय (halogen exchange) अभिक्रिया को दर्शाती है?

Consider the following statements about SN2 reactions: 1. They are bimolecular reactions. 2. They proceed with complete inversion of configuration. 3. They involve the formation of a stable carbocation intermediate. 4. No carbocation rearrangement is involved in them. Select the correct answer from the options given below.

Predict the major product when 2-bromobutane reacts with alcoholic KOH under heating conditions.