Option 1 -> Past continuous doesn't connect the past action to the present and doesn't work with "since."
Option 2 -> Present perfect simple correctly expresses completed actions from past to present with "since" and specific countable instances "once or twice."
Option 3 -> Present perfect continuous suggests ongoing duration, which contradicts the discrete, countable nature of "once or twice."
Option 4 -> Past perfect is for actions before another past action, not for actions connected to the present with "since."
Hence, Option 2: has messaged -> The present perfect tense is required here because "since" indicates a time frame from the past continuing to the present, and "once or twice" refers to specific completed actions within that period -> correct