Static and triggered abilities are unaffected by Hold for Questioning.

Loyalty abilities are a type of activated ability, so Hold for Questioning will prevent an enchanted planeswalker's loyalty abilities being activated.

Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities and will have colons in their reminder text.

The permanent can be untapped by other spells and abilities.

You can enchant a permanent that is already tapped with Hold for Questioning. If you do, it doesn't become tapped again, but you will still investigate.