Skills and Items help needed

I need some help answering these three questions please in MV:

1 - How do I create a skill that randomly damages either the target or the user, which is affected slightly by luck?

2 - How do I create an item or skill that takes time to have an effect (e.g. a potion that takes two turns to drink in battle) but with them not taking time to use outside of battle?

3 - How do I create a bow that uses an arrow every time you attack, or use a skill involving a bow, that you cannot use with no arrows?

Many thanks.

You can use common events for all of these effects and then call the common event when the ability is used.

For example, on the first skill, you need 3 separate skills, one to run the common event and one for each effect.

The common event would set a variable to a random number, we'll say a number between 1 and 100. Then it'll add, lets say, 10% of the LUK stat to that variable. Then do a conditional branch where if the variable is 50 or higher, then it uses the effect that damages the enemy, otherwise it uses the effect that damages the user.