Coding and Decoding Questions

If REGAINS is coded as QDFZHMR, then how will PRY be coded as?

In a certain code language, "INSTANT" is written as "IOUWESZ". How is "FORGET" written in that code language?

If BOULDER is coded as ZMSJBCP, then how will ELK be coded as?

In a certain code language, "RAIN" is written as "OHBQ". How is "SUMMER" written in that code language?

In a certain code language, "OPTIMIST" is written as "LKRNRGHG". How is "PESSIMIST" written in that code language?

If 4 x 5 x 2 = 524, 3 x 7 x 2 = 723 and 6 x 8 x 7 = 876 then 9 x 4 x 5 = ?

If QUICKLY is coded as OSGAIJW, then how will HUE be coded as?

In a certain code language, "COPIOUS" is written as "2345389" and "GENEROUS" is written as "16760389". How is "PIGEON" written in that code language?