No, all upper division business courses, except for UGBA 194, 198 and 199, must be taken for letter grade regardless of whether or not you have completed the 38 upper division business units.
Yes, you can as long as no more than 1/3 of your total UC units are P/NP when you graduate. You should be aware that in order to qualify for “Honors at Graduation” you must have 43 letter graded units as well as meeting the GPA requirements.
After you become a senior (with 90 semester units earned toward your BS degree), you must complete at least 24 of the remaining 30 units in residence at the University in at least two semesters. To count as residence, a semester must consist of at least 4 passed units. You may use a Berkeley Summer Session to satisfy one semester of the senior residence requirement, provided that you successfully complete 4 units of course work in the Summer Session and that you have been enrolled previously in the Haas School. Students interested in International Study will discuss this requirement with an advisor.