... it is really wierd there is not any patch or plugin for it.
It's not weird, actually. Typically, changes and features are introduced only into current Opera versions as Opera goes along... so versions previous to an added change are considered to have been superceded and essentially are no longer supported. Because you have a hardware limitation (lacking SSE2), you're unable to use Opera versions later than v20... which is an unfortunate reality in a changing-technology world. All equipment and operating systems become obsolete in certain ways over time, and that obsolesence has consequences felt by users. This is just one of them.
As far as plug-ins are concerned, if there's nothing currently available, that's unlikely to change, since almost all other users are upgrading Opera as new versions emerge and are "pushed" out to users via auto-updating. Hence there's no "market" justifying a developer's investing time/effort into trying to code a plug-in/extension for an obsolete situation or version - there's no real future in it.
Yeah it is logical that its not going to happen anymore, but why someone was not developed way to force to opera show full url while that feature was missing during versions 15-20 when they was new... thats kinda magic for me 🙂