Short - How to Install a 2 Post Car Lift 

But when can we go ahead

This is that same lift www.redlinestands.com/catalog/lifts-c-290/automotive-lifts-c-290_138/2-post-car-truck-lifts-c-290_138_139/kernel-9k-tp9k-x-series-clearfloor-2-post-lift-p-920

Depends entirely on the lift and capacity. Always check the owners manual.

Exactly. If your slab is 4" thick you'll have a car on its roof!!

He doesn't sound like the character Morty.