A: No. The UPD is only needed if your base ZIP contains SP0. Look for a "Full Integrated" ZIP that says "SP6 included."
WARNING: CATIA is proprietary commercial software. A single license for V5R21 historically cost between $10,000 and $30,000. There is no "free" official download. However, many students, legacy users, and hobbyists look for archived copies. catia v5 r21 zip file upd download
Contact an authorized CATIA reseller. R21 is an older release (circa 2011); current versions include V5-6R2023 or newer. Older versions may still be available for legacy support. 000 and $30