Order of reading surahs in salaah

if I read surah Alam Tara Kaifa………….in the first rikat of any namaz say fardh,sunnat or nafil namaz can I read surah Teen( Wat teeni waz zaitoon..) in the second rikat. Some say it is reading the quran backwards. So will my salah be in-valid or is it ok to read it my salah will be valid.What if someone purposely or forgetfully read these in any salah.
Please avoid confusion.
Jazzak Allah!