Can I run lot of devices in free version ?

Yes, but only for personal use and with limited features. The free edition is not described as having a strict device-count limit here, but it is meant for personal use only and technical assistance is not available. The free plan includes Android 5.0 to 15.0 and only a limited set of widgets like GPS spoofing, screen capture, battery, call/SMS simulation, Android identifiers, Google Play Store, and storage speed: Genymotion Desktop, Get Started with Genymotion Desktop