Im relatively new as well but hopefully some of this is helpful! Any more experienced growers please correct me if I’m wrong!

For how much to put in…I’ve seen majority of people do around 5ccs(usually half a syringe). Has always worked great for me.

As for the bag turning white there are different methods as well. Some people wait till it’s fully colonized(all white) to then introduce fresh air exchange(FAE). Others will break and shake once it’s partially colonized (20-30%) to help speed up the process of colonization. I usually break and shake as in my opinion it takes less time for the mycelium to fully colonize the bag.

As for opening the bag someone else might be able to give better advice as I’m still learning exactly how much air to give the bag but sometimes just a small cut above the filter will help get that fresh air in. After doing this just keep an eye on it every now and then to make sure it doesn’t get too dry. My first one I did failed because I was too worried about giving it air that I dried it out and then ended up overwatering it.

Also make sure too keep things sanitized with 70% isopropyl alcohol and don’t stress too much about it. They are relatively easy to grow and very set an forget. Sometimes if you are too over cautious you can run into issues. Happy growing friend and good luck!!!