1. Is it correct to say "Do you have class today?" Yes, that's fine.
? Or should it be "Do you have any class today?", No
"Do you have classes today?" ? That's okay too.
How about "Do you have school today?" ? Just fine.
2. Can "I missed you" also mean "I miss you" as in "I haven't seen you for a while and I want to see you soon"?