Does God know everything?

Yes.  He knows everything that has happened, everything which is currently happening, and everything that will happen (Is. 46:9-10).  He knows our thoughts and what we will say before we say it (Ps. 139:1-4).  He knows how many stars exist and “his understanding has no limit” (Ps. 147:4-5).  Sometimes we unjustly judge ourselves, but God “is greater than our hearts, and he knows everything” (1 John 3:20).