The 25 A continuous rating is the breaker's thermal current. The ETU850 electronic trip unit lets you set the long-time pickup anywhere from 38 A to 300 A. Operating temperature range is -25 °C to 70 °C, with no derating needed across that span — the 25 A rating holds at every temperature from 40 °C through 70 °C (–).
That 86 mm depth is the can depth — it fits standard MCCB mounting footprints in switchboards and panelboards. Four poles means it needs four line-side and four load-side lug connections; the neutral pole is switched, so it's a full 4-pole disconnect for three-phase-plus-neutral systems.