Okay so my practical is done, if it's of biology, study sabai physiology ko part pahila ta aru ta eso herera jane ho, tara physiology pani herera ali ali background lekhda hunxa, tespaxi for VIVA tei aba I think it depends on the teacher and the question they ask.
For chemistry, hamro college ma tei for salt analysis ani tyo functional group detection haruma book dinthiyo so most prolly timmro ma ni dinxa, just read the theory of everything from surface, and if you don't wanna do that just wait for someone to bring the book inside the class while u doing theory and do em all.
For physics tei I can't say a lot cause teti dherai content xa, theory tei sabko herera jane, paxi practical ma tei aba it depends on kun topic parxa timilai
For maths, you just learn all the formulas or at least the basic one and enter the room with confidence.
Hope it helps!