  We report multi-wavelength study of a complex M-class solar eruptive flare
that consists of three different sets of flare ribbons, viz. circular,
parallel, and remote ribbons. Magnetic field modeling of source active region
NOAA 12242 exhibits the presence of 3D null-point magnetic topology which
encompasses an inner bipolar region. The event initiates with the faint
signatures of the circular ribbon along with remote brightening right from the
pre-flare phase which points toward the ongoing slow yet persistent null-point
reconnection. We first detected flux cancellation and an associated
brightening, which are likely signatures of tether-cutting reconnection that
builds the flux rope near the polarity inversion line (PIL) of the inner
bipolar region. In the next stage, with the onset of M8.7 flare, there is a
substantial enhancement in the brightening of circular ribbon which essentially
suggests an increase in the rate of ongoing null-point reconnection. Finally,
the eruption of underlying flux rope triggers ``standard flare reconnection"
beneath it producing an abrupt rise in the intensity of the parallel ribbons as
well as enhancing the rate of null-point reconnection by external forcing. We
show that within the the fan dome, the region with magnetic decay index n>1.5
borders the null-point QSL. Our analysis suggests that both the torus
instability and the breakout model have played role toward the triggering
mechanism for the eruptive flare. This event is a nice example of the dynamical
evolution of a flux rope initially confined in a null-point topology, that
subsequently activates and erupts with the progression of the circular -- cum
-- parallel ribbon flare.
