Which letter should be 7th to the right of the 12th letter from left, if first half of the alphabet series is reversed?

Which letter-cluster will replace the question mark (?) to complete the given series?

ABCD, HGLO, OLUZ, VQDK, ?

Which letter-cluster will replace the question mark (?) to complete the given series?

VTHJ ? TRJL SOKM  RPLN 

Which letter-cluster will replace the question mark (?) to complete the given series?
 CZNM, FXOL, IVPK, ?, ORRI

Which letter-cluster will replace the question mark (?) to complete the given series?

MDSA, KERC, ?, GGPG, EHOI

Which letter-cluster from the options will replace the question mark (?) to complete the given series?
 ASDF, BUGJ, CWJN, ?

Which letter-cluster will replace the question mark (?) to complete the given series?
 ZFOE, PYUA, FRAW, VKES, ?

Which letter cluster will replace the question mark (?) to complete the given series?
 ETRE, AZJG, WFBI, SLTK, ?