You'd rather deal with the spring debris than the exponentially growing algae once it warms up IMO.
The cover needs to be open to SLAM to allow the sun to burn off the CCs produced by the process.
Mix for a full day before adding CYA, salt or CH. They had all winter to stratify and are slow to mix.
It's plenty late in the season by you to fire up the equipment with no freeze concerns.
When you do open :
1) mix
2) get CYA to 30
3) get PH to a low 7
4) SLAM Process
4-A) the crud needs to go, because it'll chew through chlorine. The process will lighten the pool so you can see more crud on the bottom. Scoop and vac blindly doing your best to maintain a pattern until then.
That is super helpful to know. I 'soft opened' my pool yesterday and put in a punch of liquid chlorine, letting the pump circulate it because it's already green. If i don't take the cover off it won't get clear? I was planning on doing it in a week when i had an extra set of hands since the cover is such a bear to manage by myself.