I will write melody and lyrics to your music with guide vocals only

No. You need a producer or arranger to do that.

No. My rough mixdown is a guide on how your performer would sing it. All my previous songwriting (published) works are edited, mixed and mastered by producers/ clients' producers. I can refer you to producers if you need help with mastering.

Yes. As the purchaser/producer of the master recording - you own the rights to the recording. Sell & and use it as you like. Songwriting royalties are collected by publishing firms or FILSCAP/ASCAP for the contributors. I retain my songwriting credentials copyright. PM for ghost-writing projects.

(ASCAP) American Society of Composers, Authors and Publishers & its Philippines counterpart FILSCAP are performance-rights organizations that protects musical copyrights music via broadcast or live performance and compensates accordingly.