It depends on skill sets and salary range. No, you may use as many as you like. No, we can negotiate for you, but you ultimately make the decisions about your career. A r sum is the first impression you provide to an employer or recruiter. A good r sum is one that possesses the style and content to accomplish this mission.
Content is critical.
Typos or poor grammar are style killers. Proofread, proofread, proofread. Show your resume to others and have them proofread it as well. Your r sum is a reflection of you and should be absolutely perfect. Describe skills and achievements and connect them with a particular job.