Yes, you should strategically add all jobs to your LinkedIn profile. Your present profile with skills and experience gets the highest priority. Still, giving a detailed experience can add more value to the overall career journey. For freshers, you can add internships, projects, co-curricular activities and volunteer work to complement your skill set.  

While experienced, you should add all roles but details should ideally be provided for the last decade in your career. Employers gauge from the last decade about what you ideally bring to the table. You can also choose accordingly to match current and future scope to give preference and compose details to target top MNCs jobs precisely.