What criteria determines the placement of a word like "first" in the
following verse:
grk: hrxato legein proV touV maqhtaV autou prwton prosecete
lit: began saying to disciples his first beware
1) first He began to say to His disciples, beware
2) He first began to say to His disciples, beware
3) He began first to say to His disciples, beware
4) He began to first say to His disciples, beware
5) He began to say first to His disciples, beware
6) He began to say to His first disciples, beware
7) He began to say to His disciples first, beware
8) He began to say to His disciples, first beware
9) He began to say to His disciples, beware first
Some of these placements might not significantly change the meaning,
but others obviously would. Why are #1, 6, and #8 impossible options?