Can a Monk use either Dex or STR for grappling attacks?

Lucky Feat, The second use on the enemy attacks roll, which one of these statement are true?

Perception vs Investigation, more detailed answer?

Casting Wall of Ice from a Staff of Frost only costs 4 charges. Is that on purpose?

Will participating in 1 round of combat break a short/long rest?

Holy Water creation, costs the same + spell slot over buying it for 25Gp. Why?