We knew we have strong feelings for each other. But I’m not ready to be his girlfriend yet (I’m 20+) because I’m not ready to commit to a long term relationship. Partly because I want to concentrate on my tertiary studies, partly because I want to guard our friendship, and partly because its long distance. I’m pretty sure he felt likewise. Its also because I was warned by family and friends that he’s not an ideal guy and I’m aware of it…but we are extremely close.

He’s visiting soon and we would be going hiking with a small group of friends. How can I refrain from showing strong emotional attachment (ie show that I’m not ready for a relationship), yet not hurt him and remain close friends?

Talk to him about how you feel and hope that he feels the same way. It's better to be honest then to continue lying to him and yourself about this relationship.

If you're more friends than girlfriend and boyfriend, a friendship may be able to continue. But, most people that break up, had a strong romantic relationship, find it hard to remain friends after it's over.

Is this the same guy your two other post today are about? There really is no need to make three post about the same person.
You tell him the truth.

Is this the same person?
https://www.askmehelpdesk.com/dating/guy-friend-turned-rather-silent-after-hinting-love-697970.html