OJ 287 is a prototypical yet very dynamic BL Lac object and is one of the best-investigated sources in different energy bands. In the time domain, apart from the typical stochastic variability of blazars, it shows a regular ~12-year quasi-periodic outbursts in optical which has been used to claim it to be a precessing binary supermassive black hole system with masses ~1010 and 108 M⊙. On the contrary, radio VLBA studies show a ~22-year period and argue for a precessing jet-disk system. In the spectral domain, the X-ray and MeV-GeV γ-ray emission is argued to be a result of synchrotron-self Compton, though contrary observational claims also exist. We present the multiwavelength study of OJ 287 from Nov 2015 to September 2017 which revealed it to be in a new spectral and temporal activity. Broadly, the temporal activity can be divided into two periods: (a) Nov 2015 – May 2016 when simultaneous variation is seen from optical to MeV-GeV (Fermi-LAT band) γ-ray energies, and (b) March 2016 -- July 2017 with intense NIR to X-ray variability but without any activity at MeV-GeV energies, and the very first detection at very high energies (VHEs, E > 100 GeV) by VERITAS. The broadband SEDs during the first period shows a thermal bump in the NIR-optical region and a hardening in the MeV-GeV γ-ray spectra with a shift in its peak. The thermal bump feature is consistent with the description of a standard accretion-disk associated with an SMBH of mass ~ 1.8x1010 M⊙ and appeared first in May 2013, around the impact time predicted by the binary SMBH model. At the same time, the γ-ray emission can be naturally reproduced by inverse Compton scattering of photons from the broad line region which has been seen during the close encounter duration of the binary SMBHs, thereby settling the source to be a binary SMBH system as well as MeV-GeV emission to be from inverse Compton of BLR field. This also established the emission region location to be at sub-parsec scales, contrary to previous claims. For the second duration when the source was, for the very first time, detected at VHEs, the SEDs are a mixture of typical OJ 287 SED with hardened/modified MeV-GeV γ-ray spectra and an HBL SED and can be explained in a two-zone model, one located at sub-parsec scales and other at parsec scales.