Can it be mounted on either side

Yes. The 8500W will mount on either side.

Does it come with the sensors at the bottom

Sensors are included. This is a complete unit with everything needed for installation.

LiftMaster 8500W-267 Elite Series Jackshaft Garage Door Opener

Details

The ultimate garage access solution, designed to optimize space. LiftMaster’s most advanced wall-mount opener optimizes garage ceiling space overhead, opening up possibilities to what your garage can become. Fully equipped with must-have features including built in Wi-Fi® for smartphone control, MyQ® Remote LED light, Integrated Battery Backup and the Automatic Garage Door Lock.

All LiftMaster Openers, Operators, and Systems should be purchased through a Dealer and professionally installed.

Features:

Built-in Wi-Fi for the easiest way to connect the garage.
MyQ mobile app allows you to receive alerts and control the opener from anywhere.
MyQ Remote LED light can be placed anywhere to provide bright, maintenance-free illumination.
Works with MyQ; core features that allow you to control your garage door from anywhere, get activity alerts and set schedules are included with the MyQ app.
Linking MyQ to partners apps to provide more enhanced garage control options such as voice control and geofence closing. Subscription fee applies after 30-day free trial ends. Visit liftmaster.com/mypartners for more details.

Performance:

Wall-mount design and quiet DC motor eliminate noise and vibrations through the ceiling providing smooth operation.
Heavy-lifting power operates doors up to 850 lbs.
Integrated battery backup ensures access even when the power’s out.
Warranty lifetime motor, 5-year parts, 1-year battery and accessories.

Safety and Security:

Included automatic garage door lock makes the garage door virtually impenetrable.
Timer-to-close automatically closes the door after a preset amount of time.
Security+ 2.0® sends a new code with every remote control click.
Motion detector automatically turns on the light.
The Protector System® auto-reverses the door if there’s an obstruction.

Included Accessories:

MyQ Remote LED Light (827LM) Operates automatically with the opener and works with the MyQ App.
Integrated Battery Backup (485LM) Powers up the opener when the power’s out.
Automatic Garage Door Lock (841LM) Deadboldts the garage door automatically every time it closes.
Two 3-Button Remote Control (893MAX) Operate up to three garage door openers or MyQ Light accessories. Compatible with all LiftMaster Garage Door Openers manufactured since January 1993.
Keyless Entry(877LM) Operate up to 24 garage door openers.
Smart Control Panel® (880LMW) LCD display enables simple programming and adjustment of settings.