You need Custom Firmware (CFW) like PRO-C or LME Infinity. A stock PSP cannot run custom Eboots (only official PSN purchases).

Let's be blunt. Sony never released Tekken 2 as an official PS1 Classic on the PSP store outside of Japan and the US briefly in 2007. If you missed that window, your only way to legally play it on PSP today is to own the disc and rip it yourself. The "abandonware" argument is tempting, but Namco (Bandai Namco) still owns the copyright.

The Ethical Rule of Thumb: If you currently own Tekken 2 on PS1, PS3 (via PSN), or the original disc, creating a personal Eboot for your PSP falls under fair use for format shifting. Do not distribute your EBOOT.PBP file on torrents.

Before diving into technicalities, let's address the appeal. Why go through the hassle of creating an Eboot when you could play Tekken 7 or Tekken 8?

Perhaps your memory stick is faulty, or you cannot find a clean rip of Tekken 2. What are your options?