Can i control 2+ instruments on 1 laptop with MainStage 3?

I have a Mainstage 3 on a Macbook Pro, and Lexicon LambDa with 2 audio inputs and a midi port.

In Logic Pro ... I can record a guitar on one track with input 1; while a microphone on another track with input 2 and a keyboard all at the same time. I can control each track volume in a single instance of a mixer board. I'd like to utilize Mainstage in the same capacity for a live performances.

Can i have a guitar, microphone and keyboard running through a single instance of Mainstage 3? if so, how do i add a guitar rig or microphone to a keyboard session of Mainstage?

I've tried to open 2 different Mainstage windows (1 for guitar and 1 for Keyboard), but once i click on the keyboard window, the guitar is no longer heard.

do i need 3 laptops to utilize Mainstage for a keyboard, guitar and microphone live performance?

Thnx

dekanu