Can I start in Lightroom Classic to use brushes then move to Lightroom CC to use presets?

What do you mean you want to use brushes? Lightroom CC has essentially the same brush for making local/selective edits that Lightroom Classic has, and almost the same complete set of editing tools (though not the same set of supporting edit features.

To work with an image in both: assuming that Lightroom CC is your starting point and your image is there, open Lightroom Classic, enable syncing by clicking on the logo area in the top left and making sure it's turned on. Your LR CC photos will appear in Lightroom Classic and work you do in one will sync to the other.  However, there can be complexities in using both and it is not generally recommended, so be sure to do more research on this topic (Google "can i use both Lightroom CC and Lightroom Classic"). Since you're a beginner, I would suggest instead first spending time learning one of the programs well.

Just sync the Lightroom Classic catalog to the cloud and add the images you want to work on to a synced collection.