Are all the Society gate hoarding advertisement display which we see in cities like Delhi, Hyderabad, Mumbai, Jaipur legal?

No. The menace of illegal billboards and RWA gates is somewhat present in Indian metro cities. However municipal corporations and local administrative bodies carry out crackdown on such illegal ads in Delhi, Mumbai and Jaipur at regular intervals to safeguard the interests of advertisers who pay genuine taxes and install ad creatives on sites after fulfilling all due requirements.