about cancelling a give-away

Just delete it, it is automatic before end.

Few people care.

There is a topic called the perpetual i need 5 entries or something like that. You can tell people there that you need entrants. Other than that, I'd wait it out in your place. In the last hour or minutes many people join most of the giveaways, it migth well work out.

You will lose one giveaway slot when you delete a giveaway, but on your level this should not be an issue. Other than that there is no penalty for deleting a giveaway. Also, all participants will have their points back when you remove a giveaway.
PS. If there is no entries at all - you can as well just wait till the end of giveaway, it will end without winners and that's all.

How do giveaways effect your resume? What am I missing here?

Well, as others said it's not against any rule. Just wanted to point out that I have been blacklisted in the past for deleting a giveaway.

Like others said. If you submit ticket to delete GA when it's still running you will lose GA slot and winners will recover their points, even when it pushes them above 400.

You will also lose one GA slot. And if you keep deleting GA "bc not enough entries" we will not give them back to you. Normally users that run out of slots can ask for some extra slots, but they can't make GA with intention of deleting it, and then ask for slots back. That's always problem in small groups and users need to accept there is risk their GA will not get enough entries.

a good pro tip is to make a blueheart giveaway and use the "i need 5 entries" discussion to temporarily add people to your whitelist and get 5 entries. However, it's not technically a group giveaway and probably won't count as a group-specific giveaway, if your group enforces monthly GAs. Not a part of such groups but thought about making a couple of whitelist GAs in the way i described

I’ve messed up. Was not aware of this rule. I created multiple giveaways for spare keys that I had from Humble Bundle. After creation I noticed that the keys are region locked. So i deleted them all in hope of creating them again but adding the region restriction. Unfortunately I cant now because I have this restriction that I have no more GA slots. It seems I’m completely locked from creating GAs. I have opened a ticket but no reply so far.