Hello @JeremyECrawford ! I could use your expertise on rules regarding the Artificer.
Question 1: Can an Artificer use multiple infusions on one item?
Question 2: Can an Artificer use the same infusion on multiple items?

— The Kind GM (@TheKindGM) March 9, 2019

I have MANY questions, but just in case I can’t make it:

What’re the guidelines for what spells should be on its list? I’m hoping to add some XGtE spells to it. That one's easy: I plan to include a list of those spells in a future UA. 😘

— Jeremy Crawford (@JeremyECrawford) March 5, 2019

What was the purpose of giving Artificer’s something that’s going to be exactly extra attack 99.9% of the time (since they can make their own magic weapon) instead of just giving them extra attack? Were you worried Artificer’s would exploit regular Extra Attack? Playtesting. We're experimenting with a class-favored version of Extra Attack, which ties into the class's theme: magic through objects. Playtest feedback and our own tinkering will determine whether the feature survives in its current form.

— Jeremy Crawford (@JeremyECrawford) March 5, 2019

Is this the final version? I really love the idea of artificer, now as much as I did back in 3.X, but this feels like it still needs some tweaking.

— Stephen McDonald (@McFast_Food) March 9, 2019

Unearthed Arcana is unofficial D&D content. That content becomes final and official only when it appears in a D&D book or if we announce otherwise.

For more information, see the section called "Playtest Material" at the top of the artificer article. #DnD https://t.co/iqb7sxykuG

— Jeremy Crawford (@JeremyECrawford) March 9, 2019

For the Artillerist, is the turret intended to get a modifier to hit based on your modifier or is it not mentioned because it doesn't?

— Todd (@fmacanadaguy) March 2, 2019

If a rule in D&D has you make a spell attack, check out the rule on making spell attacks in the "Attack Rolls" section on page 205 of the "Player's Handbook."

Short form: a spell attack roll uses your spellcasting ability modifier + your proficiency bonus. #DnD https://t.co/gqG2mPI4Wc

— Jeremy Crawford (@JeremyECrawford) March 5, 2019

INVENTORS!
The artificer, a master of magical invention is returned with Arcane Science, Alchemist, Artillerist and Infusions… and a new spell.

DOWNLOAD:
https://media.wizards.com/2018/dnd/downloads/UA-Artificer-2019.pdf

The new version of the artificer class emerges from the D&D workshop in today's Unearthed Arcana!

These magical inventors have an unmatched versatility, and we have more planned for them ahead. You can download the class here: https://t.co/Uzzqx9ym2P #DnD pic.twitter.com/NCsCfMw8W1

— Jeremy Crawford (@JeremyECrawford) February 28, 2019

No, don’t double a double

— Mike Mearls (@mikemearls) January 30, 2018