So if I tie swarm and have Youngster with Intensity thrown into the mix, can others still use his ept even if they do not have a card to flip? If not, could someone else use a focus or evade token to flip the card back?

No and no.

Youngster only works with EPTs with the Action: header.

This is a common thought, that Youngster lets ANY pilot skill be used. This is incorrect as @thespaceinvader pointed out. The card, perhaps, would have been easier to understand if written more like " Friendly TIE fighters at Range 1-3 may perform the Action: on your equipped <EPT icon> Upgrade card. "

Youngster lets you use:

• Rage
• Expert Handling
• Squad Leader
• Daredevil
• Marksmanship
• Expose

That's all folks. A PS1 TIE Swarm with Rage is pretty hilarious though...

14 minutes ago, Slugrage said:

A PS1 TIE Swarm with Rage is pretty hilarious though...

I like to Include Epsilon Leader TIE/fo in the list to help mitigate some of the stress.