can an iphone x go in water?

Only if you plan on going no deeper than 3 inches. Now, I wouldn't recommend trying that, and it isn't warrantied anyway. Apple is making an effort to improve water resistance but it is not something they guarantee.

About splash, water, and dust resistance of iPhone 7 and later - https://support.apple.com/HT207043

Liquid damage to iPhone or iPod isn't covered by warranty - http://support.apple.com/HT204104 - "iPhone and most iPod devices are equipped with Liquid Contact Indicators (LCIs) that you can see from the outside."

Definitely not.

Not if you want it to keep working.

No, no, a thousand times no.

Read this

https://support.apple.com/en-gb/HT207043

Absolutely not. It is NOT waterproof. It is water and splash resistant. Water resistance is not a permanent condition and the warranty does not cover liquid damage.