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No you can make blog post using the inleo interface as well as well as doing delegations and LP.

Yes exactly

What @anderssinho said. You can also "mine" Leo with Leo Miner tokens on Hive Engine.

not just threads but also regular posts and delegating HP to inLeo

no, there's a ton of ways to earn LEO

You can delegate hive power/HP to @leo.voter and will earn daily interest, paid out in LEO.